View Full Version : Plug fouling problem
20th January 2005, 21:02
My 70' Ironhead fouls plugs constantly. After riding only a few miles the bike will start to sputter and miss. Once you shut it off it wont start back up. But If you put in a new set of plugs it fires right up and runs great untill ride it again. I am looking for some possible solutions. I built this bike from a basket case so who know where all the parts came from. I was thinking the plugs were getting fouled because of improter jetting in the carb. Any help would be much appriciated.
20th January 2005, 21:08
what color are the plug tips after fouling?
do you have any smoke out the pipes?
are your rings new or did ya just use the old ones?
how bout the valve guides, new , old?
20th January 2005, 21:14
Do a compression check. Let us know what you find. If you don't know how, let us know that as well and someone will guide you thru it. My gut feeling is rings but ya won't know until the check procedure.
21st January 2005, 01:42
1) What type plugs are you using??
Heat Range?? or Number on Plug??
2) Are you using new wires or the old ones?
3) Coil New or used??
4) Points New??
5) What carb are you using??
Is it New or Rebuilt??
21st January 2005, 01:59
I'll bet by now you're sorry you asked...
21st January 2005, 02:29
that last post was great!!
21st January 2005, 06:00
aside from the above you might check for any air leaks around the manifold, and also check you plugs for proper gap (.028) is usually a good gap for points ignition.
You can check for air leaks by spraying something volatile on the intake manifold.. (starter fluid, carb cleaner) and if idle increases you've got a leak....
Hope that helps..
21st January 2005, 22:31
The compression is about 140psi in each cylinder. It has new wires, points, condenser and plugs from Harley davidson. I used the "old rings", which were not old. The motor only has 3000 miles on it since a rebuild. The only thing that is not new would be the valve guides, which I completley forgot about replacing. Can the rocker boxes be pulled with the motor in the frame?
21st January 2005, 23:09
I'd rather have heard about any bleed down. Oil can temporarily seal the rings giving a false reading. Try it again and let us know.
22nd January 2005, 00:27
if the valve guides are bad you'll know it by the white smoke cloud behind you , but if they are just starting to ware it can cause oil fouling without a smokescreen
22nd January 2005, 00:44
I read the initial Post as a Fuel Fouling problem .......
Which is it?? Fuel (wet) or Oil fouling??
If Fuel Fouling...
What Carb are you using?? Mikuni, S&S, Linkert, SU...??
Do you know what the jet sizes are??
22nd January 2005, 01:32
I thought it to be a fuel fouling problem becuase the carb that is on the bike is very large. It is a Screamin Eagle carb, Keihin, butterfly style. The intake opening is very large, about 44mm. When I bought the bike I was told the carb was bought and he had never run it and he was not sure what bike it came off of. So I thought the fouling problem may have been caused by the jets being too large. But The bike does smoke white, and I did not change the valve guides when I built the bike so I think I should pull the heads and check the valve play.
22nd January 2005, 01:45
I believe your overcarbureated.....
I think the 44mm is for large stroker motors and Big twins.
If I'm correct you will not be able to jet it down enough to get the results you are looking for.
I believe a smaller carb is in order....S&S 'E' for example or something in the 38mm range.
The mm rating of a carb is measured by the mm of the internal venturi of the carb and not the outside opening where the air filter mounts, which is larger.
Am I correct on this fellas???
22nd January 2005, 03:44
I'll have to measure the venturi when I get a chance. I put my old bendix carb on to see if that would solve the problem and it still fouled the plugs, so im now fairly confidant that its not the carb, or at least not the carb by it self. If I dont have to pull the motor to pull the rocker boxes im going to check the valve play in the guides tommaro. Thanks for all your help, hopefully I can get this thing fixed this weekend because its been around 80 degrees here on the central coast of California and I need to ride.
22nd January 2005, 05:12
Thats how it goes for troubleshooting.....check everything, bring it into spec and the culprit will usually rear its ugly head.....Good luck and keep us up to date....
By the way....80 degrees??......NICE!!
22nd January 2005, 05:34
That's a good question I'm gonna need to know about sometime kinda soon on my 74xlh , will the heads, and/or rocker boxes come off w/o pullin the motor(yea this is my first sporty so I'll have alot of questions from time to time), after watching a couple Ironhead threads awhile, a few of these symptoms I recognize. Nothing happening that's alarming, I cansay that it runs pretty strong, other than a dead battry, she's has'nt stranded me yet, but mine does puke from the breather tube, but up until the Puking thread, I figured that's par for an Iron, anyway I appreciate all of the info been very helpful so far....Mike 74xlh
22nd January 2005, 05:47
YES....you can remove the upper portion of the engine...namely the rocker boxes, heads and cylinders while the engine is still in the chassis.......
NOTE: You will notice that there is not as much clearance between the rear head and the frames top backbone as the front head.......
While you can remove the rocker box from the front head by itself, in order to remove the rear rocker box, YOU MUST REMOVE THE REAR ROCKER BOX AND REAR HEAD AS AN ASSEMBLY FIRST.....then you can unbolt the rear rocker box from the rear head once you have it out......
Cylinders can then be lifted off after removing the 8 base bolts
22nd January 2005, 06:19
Hey Hardly appreciate it , one more...can ya take off the oil pump w/ motor in th e frame....Mike 74xlh
22nd January 2005, 06:28
NO, not on 1976 and earlier XL's....they use the older design oil pumps. You have to remove the engine from the frame.
1977 and later XL's have the newer style oil pumps which can be removed while the motor is in frame.
22nd January 2005, 06:34
At this point I'm really not too concerned, since it only spatters normally for a little while after I add oil, if it were dry sumping would it be puking more than that...Mike 74xlh
26th January 2005, 19:23
Well I think I may have found the problem causing the fouling problem. I pulled the valves and check play and they were perfect, im talking perfect, the vavles look new and the guides must be new. So I then pulled the cylinders and sure enough a broken ring. The cylinders bores are fine, so im going to go with a set of rings and see if that will fix the problem. thanks for all of your help.
26th January 2005, 20:09
keep us up to speed my man
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