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jgc2521
5th February 2012, 00:05
Hey, I have a 2002C with the 1250 nrhs kit, stage 2 headwork, N8 cams, Ultima singlefire ignition, forcewinder intake, and SE slip ons. I have been trying to tune in my carb and havent had any luck. I have an older CV carb from my old 883 bike and decided I would slap it on while looking at the carb on the 1250. Well to my surprise, on my test ride the bike came to life as compared to the old carb. much better performance. I timed the bike at 28* a right before switching the carbs.

Before i timed it with the light I had the bike running decent, just low on power and not lively. after timing it at 28* i had a box of bolts (sound) while accelerating. with the bone stock carb it ran better.

I took apart my 1250 carb and it has a dynojet kit (?)
-adjustable needle w/ the E clip in the 4th slot from the closer end, with 3 washers closer to the end.
-emulsion tube with only 2 holes
- 45 jet
- 180 jet
- I don't know whether it has the stock slide or not.

I don't have any other jets for the carb so I was wondering if I should modify the bone stock carb or this one w the what i assume to be dyno jet kit in it.
If it is dynojet i assume it would be the 8103 kit.

The bike is running better with the bone stock kit that it has since i've done the upgrades so i was assuming getting a few jets from harley would be the way to go.

Anyways I got 2 carbs, a dynojet kit and want to make one good carb, what would y'all recommend doing? The bone stock carb doesnt even have the cap drilled out on it. I was thinking just do some test with it on there but I would value y'alls responses for the best course of action.

-Couch

patrickd
5th February 2012, 00:17
Sounds like with the rattle you might be running too much timing for the level of compression in your cyls.. When you hear that sound you're killing your engine.. Either step up the octane or retard the timing till it is quiet again.

jgc2521
5th February 2012, 00:27
Sounds like with the rattle you might be running too much timing for the level of compression in your cyls.. When you hear that sound you're killing your engine.. Either step up the octane or retard the timing till it is quiet again.

When I put the stock back carb on the rattling stopped completely. Also isn't a stock sportster set at 35*?



Also, forgot to mention. The modified carb was done by the previous owner along with him guttind the mufflers, and buying the N8's... he blew his motor and i bought his complete bike (pile o parts) for cheap cheap. I used his frame to put my built motor in and used his cams, carb, intake. I've added the singlefire later, and am just getting around to tuning this thing to it's potential.

patrickd
5th February 2012, 00:36
yes. It sounds like you prob had a plugged carb and it was running lean and causing that spark knock.

maru
5th February 2012, 00:46
Id work with the stock carb. See what it has for a pilot and a main jet and stick with keihin stuff on the new carb if possible. It sounds like you have a dyno jet needle jet. Those only accept their main jets and they are not marked the same as the oem jets. In other words a 180 main jet by dyno jet is not the same as a 180 keihin jet. Depending on how long ago the kit was made, the needle and needle jet could be prone to wear.

Put a fresh set of plugs in the thing, ride it and see how it behaves. If it is rattling with the new carb on high test, pull some timing out of it before you hurt it. If the bike runs good, don't assume you need to throw jets at it unless you have some indication that it needs it.

jgc2521
5th February 2012, 01:21
with my CR 10.5:1 i've been running ngk dpr8ea-9 at .040 does that sound right?

maru
5th February 2012, 02:18
DCPR8 - I think the stock ones are 7's. I am not sure where the DPR8's are different.

jgc2521
5th February 2012, 03:56
i believe the 8's are one heat range colder than the 7's... that is to make up for the high c/r.

XLXR
6th February 2012, 05:52
Rubbermount_EVO Carb basics and jetting by reading the plugs (http://www.xlforum.net/vbportal/forums/showthread.php?t=506958)

This thread is buried in the jetting sticky index.

Sounds like you need to understand basic tuning methods. The link above outlines such a method. However, it is slanted to rubber mounts with stock ignitions.

The rattling you hear is probably pre-ignition or detonation, which can be very dangerous because it can damage pistons. Your first step is to retard the timing to prevent it from happening.

Then do plug readings at idle, mid throttle, and full throttle to determine how to change the jetting. Once you get good plug readings at all three throttle positions, start to advance timing a few degrees at a time.

High compression engines will need premium octane gas.

You probably should go back to 7 heat range plugs. Colder plugs are not meant to cure the problems you are having. Use anti-seize on the plug threads, just a thin coat to prevent getting any on the electrodes.

Next question, does the 883 carb have the same throat size of the other carb? It is possible the 883 carb was previously jetted too rich, and it just happens to work on your 1250. At least it works better than the other carb.

Seems like a lot of people have problems with the Dyno Jet kit. Certainly, a lot of the problem is not knowing how to tune correctly from the start. If the carbs you have both have the same throat size, I would start with the one that works best because it may need nothing more than a few jets and needle. No telling how many other problems the other carb has.

jgc2521
6th February 2012, 06:40
The rattling you hear is probably pre-ignition or detonation, which can be very dangerous because it can damage pistons. Your first step is to retard the timing to prevent it from happening.

Yeah, it was detonation for sure. Once i heard it i decided to put the virgin carb on bf something happened. The virgin carb cleared it up and i looked into the dynojet carb



Then do plug readings at idle, mid throttle, and full throttle to determine how to change the jetting. Once you get good plug readings at all three throttle positions, start to advance timing a few degrees at a time.

If only it would stop raining


High compression engines will need premium octane gas.

already do


You probably should go back to 7 heat range plugs. Colder plugs are not meant to cure the problems you are having. Use anti-seize on the plug threads, just a thin coat to prevent getting any on the electrodes.

OK, please explain. don't take me the wrong way i want to learn. these were just the plugs that Dan had recommended for what i have so i took it as gold.


Next question, does the 883 carb have the same throat size of the other carb? It is possible the 883 carb was previously jetted too rich, and it just happens to work on your 1250. At least it works better than the other carb.

the 883 is virgin, i haven't looked to see what jets are in it. But it does work better from the short ride i have made since the switch


Seems like a lot of people have problems with the Dyno Jet kit. Certainly, a lot of the problem is not knowing how to tune correctly from the start. If the carbs you have both have the same throat size, I would start with the one that works best because it may need nothing more than a few jets and needle. No telling how many other problems the other carb has.

I assumed the throat size is the same. They both fit in the same intake manifold, and are both factory carbs. one is off of a '95 883 hugger and the other off of a 2002 1200C

I'm more of a diesel guy. I know my way around motors, just never really dealt with hopping up a bike before.

I plan on riding the bike with the virgin carb for a little while with fresh plugs to see how they look. Then getting new jets from there.

Do i need to be worrying with the timing since i'll be changing the jets and all. right now I have it set at 28* that was with the molested carb.

I also adjusted the voes after building my engine, I just can't remember what i set it at. I went with something that I found on here so hopefully it's good for now.

Thanks for the in depth reply!

XLXR
6th February 2012, 06:57
OK, please explain. don't take me the wrong way i want to learn. these were just the plugs that Dan had recommended for what i have so i took it as gold.

Dan at NRHS? His guess about the correct heat range for your build should be way better than mine.

You may have multiple problems. Improper timing and improper jetting, at the least. If you don't have extremely high compression, by retarding the timing, and going to a richer mixture in all 3 throttle positions, my guess is you should be able to use the standard heat range spark plug. Once you get proper jetting / plug readings, advance your timing a bit. Then you may, or probably will, have to go to richer jetting. Then increase timing a few degrees again. Repeat as needed. Once you get the timing and jetting somewhere close, then start looking at the spark plug heat range.

However, if you have an extremely high compression, starting with the colder heat range may be safer. If they turn out too cold, you may have to go back and advance timing.

I have not worked on a frame mount bike with VOES, so I do not know the specifics about timing adjustments, but the general concepts apply to all motors.

I just found and added some good information about spark plug heat range to my link in the post above. Timing, jetting, spark plug heat range, compression are all closely related.

jgc2521
6th February 2012, 07:08
appreciate it!

maru
6th February 2012, 10:34
The 8's are the common heat range for a warmed over engine, but I would double check the other info on the plug, my notes show a slightly different listing and i am not sure what or even if there is a difference. Run the best gas you can in it and if it shows any evidence of rattling, pull timing. You can drown it with fuel but generally that is not the way to go. Don't worry about the actual numbers, go with what the engine wants.

If you have a choice of several possible advance curves, don't assume the most aggressive one will make the most power. In many cases it is the least aggressive that makes the most power.

What does the bike have for heads, are they worked over 883 heads or 1200 heads?

jgc2521
6th February 2012, 16:47
what does the bike have for heads, are they worked over 883 heads or 1200 heads?

883

maru
6th February 2012, 22:56
Flat tops or dished conversion pistons?

jgc2521
6th February 2012, 23:06
flat top........

jgc2521
6th February 2012, 23:18
these are some plugs i just took out. They have been in for a while now and have cleaned up since putting the newer carb on. they were much richer looking before.

http://i742.photobucket.com/albums/xx69/jgc2521/1fb2f61b.jpg

http://i742.photobucket.com/albums/xx69/jgc2521/482b4885.jpg

jgc2521
6th February 2012, 23:19
putting some more ngk dpr8ea9 gapped at .040 and will try to take some more pics tonight after a little ride. won't be able to do the 3 step method, but just a short ride overall look

madnss
6th February 2012, 23:29
A man that can run a dyno and tune will save you a lot of headache if you have the break in miles done. $200 bucks to tune a pricey motor is cheap!

maru
6th February 2012, 23:43
I ran a few numbers on your build and in order to do that, I made a few assumptions. I assumed a 3.563 bore and a 3.1825 stroke since you have a 1250. I assumed a .040 head gasket and zero deck height for a squish of .040. I included a 44 DEGREE intake close for your cam set. I assumed a 49cc combustion chamber for your 883 heads, but that could be incorrect depending on chamber work and valve reliefs, valve sinking- etc. I assumed a sea level altitude.

Given the assumptions I made, I came up with a static compression ratio of 11.9 to 1 - a corrected compression ratio of 10.7 to 1- this factors in the bleed-off given the timing of the intake close and is the more critical number in a street engine. These calculations yield a theoretical cranking compression of 230 psi at Sea level. You could do a compression test to verify some of my assumptions. This number is high enough to give you some fuel sensitivity. Not so high that it won't work but high enough that you should be paying attention to things. High test fuel only for sure. Check new plugs on the porcelain for any sign of detonation and pull timing if you hear or see signs of it. If you have a choice of timing curves, run the mildest advance curve. If the bike is fine in the cold weather, do not assume it is fine in the heat of the summer. I would not pull timing as a preventative measure but If it rattled under load, I would pull timing. I would not try to drown detonation with fuel but it is sometimes possible to do that.

Remember that each line on your timing plate represents 5 degree's- a little goes a long ways.

Your last set of plugs were rich somewhere for sure. When you test ride it, slow it right down and run it hard enough to give it a chance to rattle. Hills can be helpful. Sometimes detonation will show up as tiny silver speckles on the porcelain. They may be hard to see if the mixture is to rich. Don't expect to see much color on the plugs if it is close with current no lead fuels.

jgc2521
7th February 2012, 00:02
i can look and see if dan has it detailed on the receipts. And yes i'm in louisiana so sea level. bike won't leave sea level... upon further inspection i noticed the accel pump wasn't working on the "good carb" so i switched the diaphragm with the other carb. also drilled the mixture screw and checked... it was only 1 turn out, i backed it out to 2. but will do the check on it.

rocketmangb
7th February 2012, 01:13
Might check those plug numbers as I am not sure what you are running
Stock NGK would be DCPR7E gapped 38 to 43
I run 8's which are one colder and should be fine for your bike.

Can you do a compression test ?

If so,its throttle wide open and slide wide open !

jgc2521
7th February 2012, 01:28
http://i742.photobucket.com/albums/xx69/jgc2521/be650b4a.jpg
http://i742.photobucket.com/albums/xx69/jgc2521/1977e453.jpg
http://i742.photobucket.com/albums/xx69/jgc2521/c961f0d8.jpg

this is after a few hard runs and cruise through town. what's the verdict?
Dan had said that i'd have around a 10.5:1 C/R with the head job and pistons but i'll try to find paper work to double check. i was thinking the idle was a little rich so i went to 1.5 turns, this was after the pics though, and no riding to check it.

maru
7th February 2012, 01:31
Rich somewhere but if you are running drag pipes, they could be super rich at one point due to reversion and lean elsewhere. Drag pipes can cause reversion big time with any kind of overlap.

Do a compression test, that will give you some indication of what you have for compression. Any indication of detonation?

jgc2521
7th February 2012, 02:30
If you have a choice of timing curves, run the mildest advance curve. If the bike is fine in the cold weather, do not assume it is fine in the heat of the summer. I would not pull timing as a preventative measure but If it rattled under load, I would pull timing. I would not try to drown detonation with fuel but it is sometimes possible to do that.


I'm on the second to mildest curve. on the ultima. it seems good. would running the mildest be for safety?

i didn't get to lug it down hard. i did a slow rolling start in second and did a hard twist on the throttle with no problems though

jgc2521
7th February 2012, 02:36
when i get a chance i'll do a compression test. I am in the process of looking for some baffles for these gutted screaming eagle slip ons. I don't have the free money right now for pipes, so I'm trying to get the best i can with the littlest money.

I would like to get some kinda baffles or something in there though cause like it is now it's barely better than drags. the only thing making it better is the crossover tube. any suggestions?

by the way i appreciate all the help. I wish i could by y'all lunch. the bike already runs 10x better than it did with the dyno carb.

rocketmangb
7th February 2012, 02:37
It looks rich on the pump

That top thread should clean up

I done see any anti sneeze ?

jgc2521
7th February 2012, 02:39
also for the compression test should i disconnect the coil? or just leave the plugs connected off to the side?

jgc2521
7th February 2012, 02:42
It looks rich on the pump

That top thread should clean up

I done see any anti sneeze ?

rich on the pump?

and should i be using never seize? I never have on the sporty

XLXR
7th February 2012, 04:03
Always use anti-seize with aluminum heads/threads.

I have no idea how plugs can be too rich on the pump? The accelerator pumps works in conjunction with the idle and mid throttle jetting/needle setting. I tune a carb by setting idle and mid throttle mixtures by reading the plugs, then adjust the timing and quantity of fuel of the accelerator pump to get a good transition from idle to mid range throttle. As far as I know, and I don't know all the different CV carbs, but the CV carb does not have an adjustment to the accelerator pump, except by changing the length of the pump rod. Regardless, do not try to adjust the accelerator pump until you have exhausted all other adjustments.

How many miles on those plugs?

It appears the center electrode is clean enough to indicate the plug heat range is good enough to burn off deposits.

The sooty, black base ring indicates too rich at the throttle position you held for the last 30 seconds before shutting off the bike. As Maru indicated earlier, your drag pipes could cause it to go lean at other throttle positions. I never knew that, but I suppose it is possible.

If your not hearing detonation, and you don't see black specs of aluminum on the center electrode after a full throttle run, your timing is probably close.

I would check plug readings at mid throttle and full throttle, then re-jet accordingly. Then try more advanced timing, (if recommended by Dan), then check jetting again. Then recheck plug heat range.

rocketmangb
7th February 2012, 04:08
Reversion is a big problem

jgc2521
7th February 2012, 04:36
How many miles on those plugs?

I would check plug readings at mid throttle and full throttle, then re-jet accordingly. Then try more advanced timing, (if recommended by Dan), then check jetting again. Then recheck plug heat range.

approx 10 miles

XLXR
8th February 2012, 05:56
approx 10 miles

10 MILES??????????? Your combustion is way way way off. The black base ring is way way way too rich, or some of the other problems are also present. Perhaps you are not riding the bike long or hard enough to burn off the carbon from using the choke. Are you sure the choke or vacum petcock valve are not leaking. Is the air cleaner clean and provide adequate air flow?

How many miles since the new rebuild? I would try to get a bit leaner idle and mid throttle to prevent excessive carbon build up as you continue to break in the engine, assuming reversion is not part of the problem at other throttle settings.

patrickd
8th February 2012, 06:46
10 MILES??????????? Your combustion is way way way off. The black base ring is way way way too rich, or some of the other problems are also present. Perhaps you are not riding the bike long or hard enough to burn off the carbon from using the choke. Are you sure the choke or vacum petcock valve are not leaking. Is the air cleaner clean and provide adequate air flow?

How many miles since the new rebuild? I would try to get a bit leaner idle and mid throttle to prevent excessive carbon build up as you continue to break in the engine, assuming reversion is not part of the problem at other throttle settings.

even normal running plugs are black on the base. You read a plug by the insulator and the electrodes.

XLXR
9th February 2012, 03:40
Carb basics and jetting by reading the plugs (http://www.xlforum.net/vbportal/forums/showthread.php?t=506958)

even normal running plugs are black on the base. You read a plug by the insulator and the electrodes.

I tend to disagree. The link above provides evidence, pictures of my plugs and a link to a Drag Stuff article on how to properly read plugs.

The plugs from my 2006 1200 look the same in the picture after 20,000 miles.

rocketmangb
9th February 2012, 03:47
Might be time for Wedge and XLXR and me self to go have a plug read party

patrickd
9th February 2012, 04:00
Carb basics and jetting by reading the plugs (http://www.xlforum.net/vbportal/forums/showthread.php?t=506958)



I tend to disagree. The link above provides evidence, pictures of my plugs and a link to a Drag Stuff article on how to properly read plugs.

The plugs from my 2006 1200 look the same in the picture after 20,000 miles.

While it is highly possible that I am not a spark plug expert , I got my plug reading info here and I'd bet you they know more about reading plugs than anyone on this forum.

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

XLXR
9th February 2012, 04:01
Might be time for Wedge and XLXR and me self to go have a plug read party

Unfortunately, most of the time we don't even speak the same language.

XLXR
9th February 2012, 04:10
I got my plug reading info here and I'd bet you they know more about reading plugs than anyone on this forum.

I haven't seen plugs that bad anywhere else but pictures. Even the "normal" picture is barely close to what I consider normal. It also gives no indication of how to read plugs in relation to jetting a carb.

maru
9th February 2012, 05:55
The plugs in my opinion indicate rich but the problem with looking at photo's and not actually riding the bike is that it is possible to be rich during reversion and be fine otherwise. If you look at a dyno pull of the many bikes with drag pipes you will see them go super fat when the thing is reverting. You really can not tune something like that out with jetting without causing problems elsewhere. Not saying this is the issue, I don't have enough info, I am not there. A look at your existing dyno pull would tell a lot even though it was with a different carb, even if it ran very differently. The reversion if it is an issue would show up with either carb. It might run worse or even be more rich with a given carb, but the reversion will be seen in both the TQ curve and the AFR curve.

If the thing is not pinging, I would not worry about that.

If the thing is running fine, not swilling fuel, and not fowling plugs, i would not necessisarily loose sleep about the jetting either.

The dyno pull might give some answers though, even an old one.

The mildest timing curve often gives the most power. It is a fallacy that these things make the most power with timing that is right on the edge of detonation.