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ironheadfred883
5th November 2011, 18:38
I have rebuilt the engine in my beloved 1962 XLB. Have had various issues with it, some of which were solved by the great advice I've received on this forum. My newest dilema is that the engine runs great when cold, but once it warms up it starts backfiring and losing power. I thought it might be starving for fuel, but I ran a drain test on the fuel line and it flows very freely. The piston clearance is correct, and the engine has about 100 psi compression in each cylinder. I've got a brand new S&S carburetor with a 0.265" intermediate jet and a 0.064" main jet (the next size up caused the engine to run rich, and the plugs to turn black). When I check the plugs they are sooty black with a trace of an oil film on them. The front cylinder plug is a bit blacker than the rear. Oil pressure is about 30 psi (at low rpm) when the engine is cold, then drops down to about 10 psi when warm. Using 10-50 Shell Hellix oil. The engine has new plugs (hot), new coil, new distributor (mechanical advance Taiwan after market no-name brand). The engine runs very smooth and has great power ... until it warms up. The pistons, and rings, are brand new after market jobs as well. Any chance the piston material is the wrong type and expanding more than it should? I'm not sure why that would cause backfiring. I'm wondering if the mechanical advance might be screwing up. Has anyone experienced a similar problem?

IronHeadFred, the 10-minute rider ...

ryder rick
5th November 2011, 18:48
Read the S&S installation instructions and correctly set your carb. http://www.sscycle.com/uploads/instructions/51-1011.pdf

Idle speed and mixture MUST BE SET HOT, and that doesn't meant 5 min hot, that means a hot oil tank.

Pay particular attention to your idle mixture settings and intermediate jet size. Your intermediate jet #'s seem on the small side, and your idle mixture screw should be between 3/4 turn and 1 1/2 turns (idle mix screw is very sensitive 1/8 turn is big). Do not try to idle the motor below 900 rpm or it may starve for oil on the pistons.

LivingCanvas
5th November 2011, 19:26
Pushrods adjustment

I'd put money on it

LivingCanvas
5th November 2011, 19:29
http://xlforum.net/vbportal/forums/showthread.php?t=44143

I like to use the looser setting given

ryder rick
5th November 2011, 20:25
Pushrod settings do not affect a hot motor. (other than noise)

If the pushrods are too tight (set hot) it may not start when cold.

78ironhead
5th November 2011, 20:49
If the pushrods are too tight (cold setting) as the engine warms up the pushrod adjustment will become even tighter.

ryder rick
5th November 2011, 21:08
If your going to argue you should have ammo.

Sorry you are wrong. As the cylinders heat up they grow, as they grow the pushrod clearance increases (since the pushrods get no where near as hot as the cylinders they do not expand at the same rate)

That is why if you set the pushrods on a hot motor it may not start cold, and the colder it gets the less likely it will start due to compression loss from the valves being held open.

And all of this is why you set the pushrods on a STONE cold motor.

LivingCanvas
5th November 2011, 21:34
Pushrod settings do not affect a hot motor. (other than noise)

If the pushrods are too tight (set hot) it may not start when cold.

I beg to differ. Coming from first hand experience, not theories on metal expansion. I had the same exact symptoms as the op and the bike was much harder, almost impossible to start (kick only) WHEN HOT. Problem solved when I re adjusted the pushrods, WITH NO OTHER CHANGES my bike was back to a good running 1-2 kick bike.

thessler
5th November 2011, 21:54
Quick thought - Is it backfireing through the carb or pipes this may help narrow it down.

LivingCanvas
5th November 2011, 21:57
If your going to argue you should have ammo.

Sorry you are wrong. As the cylinders heat up they grow, as they grow the pushrod clearance increases (since the pushrods get no where near as hot as the cylinders they do not expand at the same rate)

That is why if you set the pushrods on a hot motor it may not start cold, and the colder it gets the less likely it will start due to compression loss from the valves being held open.

And all of this is why you set the pushrods on a STONE cold motor.

The arrogance of this post is irritating, and un needed.

There are so many more variables than just the expansion rates of the jugs vs the pushrods.

FWIW mine were set on a stone cold engine both times mentioned in my post above. Set correctly and double checked.

I could really care less about theories on metal expansion and any other overly technical mumbo jumbo. In my case, I know what worked on mine and several other ironheads I have helped fix, with these EXACT SAME SYMPTOMS.

Here is an example, posted by a close personal friend. What the thread doesnt show is me bugging him everyday to adjust the pushrods, but he resisted thinking it to be something else because his started and ran fine COLD, but wouldnt start and ran like shit HOT. End of thread has him adjusting pushrods and SOLVING THE PROBLEM.
http://xlforum.net/vbportal/forums/showthread.php?t=1142456

Granted, the op here could possibly have a different problem. But my suggestion comes from a pretty good base of what has worked.

ryder rick
5th November 2011, 21:57
The backfiring is plugs fouling...

DR DICK
5th November 2011, 21:59
1st thing id go after is a bad condensor.

ironheadfred883
6th November 2011, 07:38
Gents,
I forgot to mention that I also suspected the pushrods at one time. I checked them with the engine cold and they were all easy to rotate with just a slight bit of side play. Nonetheless, I went ahead and loosened them a bit more. This seemed to eliminate a bit of top end chatter from the engine, but I'm not really sure if I'm just hearing what I want to hear due to my lack of understanding of what's going on.
The backfiring is coming out the exhaust, which could be taken to indicate the fuel mixture is too lean(?). I had the same problem with the original jets: 0.265" intermediate and 0.064" main. The smaller jet sizes helped reduce the amount of soot on the plugs, but didn't seem to have any effect on the poor performance of the engine when it warms up. I have read the S&S carb manual. I set the idle speed screw at 1-1/2 turns. The turn-in and turn-out test to find the limits of the adjustment always result in going right back to 1-1/2 turns. But I haven't tried readjusting it with the engine fully warmed up ... will give this a try (thanks for the suggestion).
The engine starts without any need of the enrichment lever. A single turn of the throttle to squirt some fuel in the carb, then a few kicks with the throttle barely open, and the engine starts. I learned this technique from advice from this forum, and I am eternally grateful for it. If I don't get it just right the "few" kicks can turn into a quite a few more kicks, and if there's too much fuel in the cylinders they can give quite a back-kick from pre-ignition. Makes me wonder if there's a problem with the mechanical advance in the Taiwan distributor. I rotated the distributor a few degrees clockwise to retard the spark and this helped reduce the back-kick tendency, and did not seem to affect how the engine runs once it starts, at least before it warm up anyway.
I think the trace film of oil on the plugs is coming from the intake valve stems passing oil. When I took the heads off for inspection I found that most of the oil was around the intake valves. I removed the valve springs and tested the valves for tightness by pulling the stems down through the guides while holding my finger over the end of the guide. This creates a very noticeable vacuum. The stems are not loose, and they move very freely in the guides. I have read that this is a common problem with this engine, and in fact I bought a set of retro-fit valve stem seals that are sold on the market to "solve" this problem, mostly because I was curious about what they looked like. I have not installed them since I'm not sure if they would not just cause the stems to eventually sieze in the guides due to lack of oil.

Lively Juan
6th November 2011, 07:57
I vote with Dr. Dick on this one. Take a look at the surface of the point contacts and see if they look pitted or like they have a pile of cinders growing on them. The condensor(capacitor is more correct) is in the system to protect the points. If the points dont look pretty evenly worn you can bet the condensor is bad. Condensors and sometimes coils will take a dump when they warm up.

ironheadfred883
6th November 2011, 12:23
The distributor, points, condensor, coil, plugs, and plug wires are all new, as well as the valves, valve guides, pistons and rings, and push rods. I agree that it seems to be either an ignition problem or a carb tuning problem, but I've never come across this sort of thing before (an engine that runs like crap as soon as it warms up). Anyway, I think I have a spare new condensor that I can try out. I have noticed that the spark isn't quite as bright and blueish as would be expected (when tested outside the engine).
Thanks,
IronHeadFred, the 10-minute neighborhood hot rodd'r ...

russzx6
6th November 2011, 13:25
a new condensor can be RS out of the box. Pushrods were my 1st thought too

IronMick
6th November 2011, 13:49
... The backfiring is coming out the exhaust, which could be taken to indicate the fuel mixture is too lean(?). ... I bought a set of retro-fit valve stem seals ... I have not installed them since I'm not sure if they would not just cause the stems to eventually sieze in the guides due to lack of oil.

Backfire from the exhaust on deceleration in a result of lean mixture, possibly because of an intake or exhaust leak. I believe any other backfire is a rich condition, unburned fuel burning in the hot exhaust.

There should never be seals of any kind on the exhaust valve stems - oil here is needed to help cool and lubricate. On the intakes they are optional; the ones i have seen are called umbrella seals - they float on the stem.

DirtyCory
6th November 2011, 14:53
The distributor, points, condensor, coil, plugs, and plug wires are all new, as well as the valves, valve guides, pistons and rings, and push rods. I agree that it seems to be either an ignition problem or a carb tuning problem, but I've never come across this sort of thing before (an engine that runs like crap as soon as it warms up). Anyway, I think I have a spare new condensor that I can try out. I have noticed that the spark isn't quite as bright and blueish as would be expected (when tested outside the engine).
Thanks,
IronHeadFred, the 10-minute neighborhood hot rodd'r ...

i have got points, condencers, and coils brand new out the box that dont work!!!!!!!!!!!!!! :censor aftermarket shit!!!!!!!!! the only ingniton stuff that i have got brand new and works well is ACCEL brand stuff. not saying there isnt more good stuff out there, just i went from tiwain aftermarket crap, then i bought accel and have never had problems since. you said you have a spare new condencer, well do you have your old one? try it too if your new one dont change things. and having a weak spark could be a sign of a weak coil. i had a coil that tested perfectly. all resistance test were withing specs of the manual. turned out, it was bad anyway. and my symptoms occured when the motor was more towards warmed up. im not sure of what your problem is, it could be several different things. but im my opionion, trial and error is a good way to get results with ignition parts. and never trust just cause you just pulled something out the box that it is up to par. especially on aftermarket shit.

ezmerf
6th November 2011, 16:27
You can also use points and condensor from 235&265c.i.chevy that would be in the 60's models these you may find american made.Make sure points are square over top and bottom if not bend till they are fully covering each other this should be done on all points.

ironheadfred883
13th November 2011, 12:59
Replaced the condensor. No difference.
Replaced the coil. No difference.
Replaced the plugs (from No.5 to No.4). No difference.
Points are new. Mate correctly. No pitting.
Disconnected the generator & regulator. No difference.
Checked the idle adjustment with the engine running hot. It's just as it should be according to the S&S carb manual.
Checked the engine compression when the engine is hot. Same as when cold (135 front, 125 rear).
Engine runs great when cold. Ride for about 10 minutes, and then it suddenly will start to lose power, cough, and sputtter, but it idles fine. Just no power. Does not backfire when deccelerating, just when under power.
Checked the plugs. They look clean, fine. No soot.
After the engine cools down it runs great again, until it warms up.
I have run out of ideas.

jharback
13th November 2011, 13:12
Sounds to me like it might be getting too much fuel. Acts as tho' the choke is always pulled out.

4camroadster
13th November 2011, 14:54
Hey Ihfred883 post a pic of your bike maybe someone will see something your not seeing!! A lot of variables apply to your problem, Could be something as simple as fuel line routing,tank venting, poor ign. circuit wiring, float level;bad float; ECT>ECT. I had a similar issue it turned out to be ign. circuit shorting on the bottom side of the dash cover!!! Post a pic !!!:wonderlan:wonderlan:wonderlan

IronMick
13th November 2011, 15:12
... Checked the engine compression when the engine is hot. Same as when cold (135 front, 125 rear).
Engine runs great when cold. Ride for about 10 minutes, and then it suddenly will start to lose power, cough, and sputtter, but it idles fine. ...

Are you holding the throttle full open during the compression test? Readings should be much higher when fully warmed up than when cold.

The symptom is classic of a clogged fuel filter. Lets thru enough fuel to idle but that is all.

ratt2y
14th November 2011, 04:43
living canvas/ryder rick.would it be a good idea to check the push rods when the bike is hot?You don,t want those push rods bouncing around like a pin ball machine.if you set them cold and they stay set thats cool.i would do what ever works for your bike.

DirtyCory
14th November 2011, 05:50
living canvas/ryder rick.would it be a good idea to check the push rods when the bike is hot?You don,t want those push rods bouncing around like a pin ball machine.if you set them cold and they stay set thats cool.i would do what ever works for your bike.

pushrods are only adjusted on a stone cold motor.

charlie walley
14th November 2011, 06:13
i work on alot,olot of bikes from h-ds to metric the majority of time 85%,are pushrod ,carb adjusment.the first thing owners do is fiddle with carb,by the time i get my hands on it ,after valves are done is do the carb settings again,after that happy customers,now in this thread im going on what the brother is writing.

ezmerf
14th November 2011, 11:13
+1 CW I sort of said the same thing.

IronMick
14th November 2011, 14:16
... would it be a good idea to check the push rods when the bike is hot? ...

pushrods are only adjusted on a stone cold motor.

+1

This gets suggested here about once every 2 or 3 years. There is a perfectly logical reason why they should be adjusted hot. However, the logic is faulty.

LivingCanvas
14th November 2011, 14:26
living canvas/ryder rick.would it be a good idea to check the push rods when the bike is hot?You don,t want those push rods bouncing around like a pin ball machine.if you set them cold and they stay set thats cool.i would do what ever works for your bike.

I always set mine stone cold and just a bit to the loose side.

Flame__
14th November 2011, 14:38
Pushrods!!!! Check them, be sure, THEN retard your timing a little and see if that helps. An advanced timing will crank good cold, then be a hard crank when warm. Your backfiring could be a timing issue.

Lively Juan
15th November 2011, 04:01
If you are going to mess with the timing at all the first thing to do is get out the timing light and watch the marks from just off idle to 2500 rpm or so then back it down to see if the advance mechanism seems to be working properly. If the timing is on with the light and the advance seems to be working you can figure that ain't your problem. Servicing the mechanical advance is never a bad idea but it isn't going to be different when warm so don't retard the timing thinking it's going to change anything.

charlie walley
15th November 2011, 04:15
plug checks not being rude ,is just that,it involves air fuel mixture,all motors showing rich at for exsample running for warm up,lean out at riding lets say50 or so ,but as always someone has it figured out,in this forum.

IronMick
15th November 2011, 04:17
... The symptom is classic of a clogged fuel filter. Lets thru enough fuel to idle but that is all.

Here i am going to +1 my own post. I have not seen anything here yet to contradict this.

Lively Juan
15th November 2011, 04:23
Here i am going to +1 my own post. I have not seen anything here yet to contradict this.

A good and simple thing to check too. I think if I wasn't finding anything drastically wrong after all this fussing and adjusting I'd be breakin' out the leakdown compression tester to tell me more about the health of the engine while it's up to temp.

sevensixteents
15th November 2011, 04:29
Will warming up cause a vapor lock?
I agree with IronMick sometimes the simplest thing (fuel filter) is oftentimes overlooked. I've had a bad coil do exactly the same thing (fresh out of the box).

I had this old 59'vw bus that seemed to always have bad condenser or bad coil etc.
No comparison of course...
I hope you find out what it is friend.
7/16

ironheadfred883
26th November 2011, 08:43
I decided to try increasing the intermediate jet from 0.0265 to 0.0280 (S&S chart shows these two sizes for an 883 engine). While I had the carb apart I found that the float level was set way too low. Came from the S&S factory this way. There was an o-ring in the needle valve seat. I took it out, adjusted the float level to 3/16” below the bowl rim, per the manual, attached the inlet line to the fuel line and let the bowl fill up. It worked fine. I was hoping I had finally found the problem. Put it all back together. It started great. Rode it 10 minutes and the same old problem surfaced again. I immediately killed the engine, shut off the fuel line, and pushed the bike home. Back in the garage I took the air filter off and looked into the carb throat while turning the throttle grip. Plenty of fuel squirted from the accelerator pump, so this at least showed the carb bowl wasn’t empty.

I restarted the engine and set the rpm to about 1500 using the idle screw. Pointed a floor fan directly in front of the bike for cooling. Engine ran great until it warmed up, then started loosing power and backfiring. Still had the air filter off, so I watched the accelerator fuel while twisting the throttle and sure enough there was plenty of fuel and it really didn’t have much effect on the backfiring phenomenon. I noticed that all the backfiring, with flames, was coming from the front cylinder exhaust pipe. The rear exhaust looked fine. No smoke from either exhaust.

So, having replaced every component on the electrical system with no effect, and having confirmed that there’s plenty of fuel getting into the engine, I thought perhaps the problem might be with the front cylinder exhaust valve. Maybe sticking, or maybe the springs are tweaked. So I figured WTF and took the heads off the engine for about the 5th time.

The first thing I found was there is really too much oil getting into the engine from the inlet valves. The inlet valve seats on both heads were wet with oil. Funny thing is, the rear head is a little wetter than the front, but the spark plug in the rear cylinder is usually a bit cleaner than the one in the front. Odd. Anyway, I removed the valves from the front cylinder head, cleaned and dried everything, then ran the valves back into the stems to see how they fit. There is very little play. If I raise the valve about 1/4 inch off its seat, just enough to hold it with my fingers, then rock the valve back and forth, I can feel only the slightest bit of play. These are new valves in new guides, but when I originally installed the guides I did not have a reamer, so instead I used valve grinding compound on the old valves and lapped the guides this way until the new valves fit (I did not use valve grinding compound on the new valves). I’ve always suspected this method probably did not result in round guide holes. But the valves mate perfectly with the valve seats and so I was hoping for the best on this.

The length of the outer valve springs is spot on with the what the book says: 1-1/2 inch. The inner springs are about 1/16 inch shorter than the 1-23/64 inch stated in the manual. All the springs are straight. Unfortunately I don’t have a way to test them under compression.

I suppose I will purchase a new set of guides and some new springs and give it one more try.

Can anyone recommend where I can purchase the proper reaming tools for the guides?

I would really prefer to have a professional mechanic do the heads for me. Can anyone recommend who I could send the heads to to have this done? Yup, I mean I would rather send the heads to the US or elsewhere than to have some local Jakarta "mekanik" get hold of them -- tried that before, with bad results.

One other alternative would be to purchase a new set of heads, or properly reconditioned heads. Can anyone recommend where I could purchase these?

Thanks and Regards,
IronHeadFred, the headless Harley rider wannabe

brucstoudt
26th November 2011, 12:59
he did say he checked fuel flow previously,right or wrong who knows?

ironheadfred883
26th November 2011, 13:11
Yes. I did check the fuel flow. I removed the fuel line from the carb and it flowed free. The test lated until about 1/2 gallon had flowed out, at which point I decided to end the test and go get a mop.

merc
26th November 2011, 14:14
I don't know if there is a dif from an EVO but I figure an engine is an engine.
My bike did the exact same thing . Shit the bed when hot. I have read that others here have had the same issue. Mine turned out to be the front plug. It looked fouled. And they were new plugs. The problem didn't happen until I tried to "tune it up" with new plugs and wires and carb adjustments. Sol I knew it was something I did wrong. I bought another couple of new plugs and that solved it. Seems the 1st new plugs sucked.
Head work can be done by NRHS or Hammer. The best in the business. Plus they help us on XLF all the time. Give them a call and at least discuss your problem with them verbally. They might recognize the issue right away. It's worth a shot anyway.

ironheadfred883
26th November 2011, 14:42
Yup. I've tried about 8 different sets of plugs, hot and cold. NGK, Autlolite, and Accel. Runs the same on all of them.

ironheadfred883
4th December 2011, 06:23
I managed to find a brand new 5/16" reamer for the inlet valve guides, but not an 11/32" for the exhaust. I'm currently waiting for the arrival of new springs and valve guides, so in the meantime I figured it would be interesting to see if my current inlet guides, which I lapped in by hand using the old valves and valve grinding compound, were within spec. I was expecting the bore to be on the high side because of the amount of oil that is getting into the intake chamber, but much to my surprise the reaming tool actually took out a fair amount of metal all the way down through the guide. With my hand-lapped fit there was a noticeable vacuum when pulling the valve out of the stem (with a finger over the top of the guide hole). Now that it is reamed to the factory diameter the vacuum is barely noticeable. This would lead me to expect that when I install the new guides and ream them to the factory setting using a proper reaming tool the end product will be a clearance greater than I had before, which ought to provide a wider channel for even more oil to flow towards the spark plug gap. But this time around I'm going to do it the way the manual says and keep my mouth shut until the results are in.

I don't know why I'm posting this. Just lonely I guess. Still searching for an 11/32" reamer if anyone has one.

IronedHeadedFred

Wooley
4th December 2011, 06:42
we use these suppliers at work. Here ya go.

http://www.mcmaster.com/#reamers/=f7lvsk

or

http://www1.mscdirect.com/eCommerce/NavigationServlet/Chucking-Reamers/_/N-77h5c?cm_re=Category-_-BodyLink-_-Chucking+Reamers&Ntk=All_MSC&Ntt=0%C2%A43438+reamer&Ntx=mode+matchallpartial&Nty=1&rawInput=0%C2%A43438+reamer%C2%A211%2F32+reamer

forqueue
4th December 2011, 09:41
http://www.ebay.com/itm/11-32-3438-8-73mm-Keystone-Hand-Reamer-NEW-Made-USA-/300618932688?pt=LH_DefaultDomain_0&hash=item45fe48e1d0

brucstoudt
4th December 2011, 18:08
sounds to me like that vacuum with the tighter clearance,could be pulling oil into the guide like a well pump.im sure theres a reason why they want an 11/32'' hole in the guide.

ryder rick
4th December 2011, 18:36
Maybe the guides were too tight and the valves were sticking open?

Intake guide clearence .0015 - .0025
exhaust clearence .0025 - .0045

ironheadfred883
18th December 2011, 14:11
Problem solved. It was the valve guide clearance.

I managed to find an 11/32" reamer while on a trip in Singapore. Had to take a taxi ride half way across the country (dang near 5 miles) to a little shop that had one that had been on the shelf so long the protective wax was cracked and dry. I think it might have been the last one for sale in S.E. Asia. Installed a new set of valve guides and reamed them per the book.

Took the bike out for a spin today and it runs fine. This is quite a milestone since this engine hasn't run for almost 15 years.

Thanks to everyone who provided suggestions to troubleshoot this problem.

IronHeadFred883

ndepratt
18th December 2011, 15:32
I want there to be a like button to hit.