took bike out for a ride and had a problem.when i got on the throttle it started to spit and sputter till i let off.i got it home and checked the simple things first.1. i pulled the plugs and noticed that the rear plug had a heavy buidup of black soot,and the front was sooting up also but not as bad.the plugs and points were from last years tuneup.2.i pulled the points cover and looked at them visually.so i cranked the motor,and noticed im getting spark behind the points plate where the weights are is that normal?i also noticed that the spark is a blueish yellow at the plugs. do i just need to do a tuneup or is there another problem? need advise on this

 

For #1, i find that the condition of the plugs is not helpful except after a fairly long ride. They will be fouled by using the choke at startup, then may need, say, a half hour or more hiway ride to clean up. I minimize this by using the choke for no more than a half a minute or so at startup, then keep it running with the throttle lock.

I am not familiar with points setups.

 

never needed to use the choke to start.always fired right up.till this problem

 

If you are in a very warm climate then not needing the choke on startup would be OK. However, if in normal circumstances the engine starts when cold without the choke then the carb is jetted too rich. I would check the pilot screw setting to ensure that the slow jet is the correct size, and that the pilot screw setting is correct.

Here are my notes ...

Setting The Pilot Screw on Your IronHead

If the carb is old and dirty the pilot screw passage may be gummed up such that you will not be able to "gently seat" the pilot screw reliably. If this is the case remove the carb from the bike and clean it up. Some guys try to do carb work with the carb in the bike. IMO this is a very bad idea.

In the pilot screw passage there should be, in this sequence: screw, spring, washer, o-ring. [Often POs have installed these parts in the wrong sequence; remember that the purpose of the washer is to protect the o-ring from being damaged by the spring]. The screw usually comes out easily. The other parts may require some work. The best technique is to stick a pipe cleaner in the hole, twist it around, and, like magic, out come the other parts on the end of the pipe cleaner.

1. You need to have easy access to the pilot screw, easy enough to reliably judge "screw it in until gently seated". Loosen the front fuel tank mount bolt; remove the rear fuel tank mount bolt; prop the rear of the fuel tank up on a piece of 2X4; on some bikes this will not be necessary.

2. With the engine cold [so you do not burn your fingers] turn the pilot screw in clockwise until it is gently seated. Count the number of 1/4 turns as you do it; write the number down. Back it out to the original setting. You may need to return reliably to this setting after experimenting.

The "normal" starting point for this process is 1,1/4 [according to the 79 - 85 FM] or 1,1/2 [according to usual practice] turns out.

EDIT: An old HotXL magazine article recommends for Keihin butterfly carbs between 1/4 and 1,1/4 turns out. My experience is that this works best. If you are more than 1,1/4 turns out your pilot jet is too small.

3. The engine must be at full warm up. It will have very hot parts; to avoid burned fingers have a well lighted, comfy place to work.

4. Set the engine idling at about 1000 RPM. You want it to be idling at the slowest speed that is consistent with a smooth idle so that you can hear or feel slight changes.

5. Turn the pilot screw in clockwise until the engine idle becomes worse; tending to stall. Count the number of 1/4 turns as you do this. Then turn the pilot screw out counter clockwise until the engine idle gets good, then becomes worse, tending to stall. Count the number of 1/4 turns as you do this.

6. The best setting for your bike will be somewhere between these two settings. The FM says to use the leanest setting [most screwed in] consistent with a good idle quality. Some guys say to go between the two settings.

It should be between 1/2 and 1,1/2 turns out from gently seated. If it is not within this range you should change the slow jet.

EDIT: I follow the advice from the old HotXL mag article - set it between 1/2 and 1,1/4 turns out.

7. You may have to adjust the idle speed.

8. Make sure that the spark plugs are clean, then ride the bike around your neighborhood for 10 minutes. Keep it under about 15 MPH so that you are on the "idle port", not the "idle transfer ports", the "mid range port", or the "main jet" [see carb diagrams in FM]. Hopefully the plugs will come out a nice medium gray or tan color. If they are too dark you can screw it in another 1/4 turn; too light screw it out 1/4 turn, and try the ride again.

9. If they are really light or really dark the problem is not with the pilot screw setting. For example, too light might mean an intake or exhaust leak, and too dark might mean the pilot jet is too large [among other possibilities].

10. My experience with this process is that after making a change i have to clean the plugs and go for a good ride [say, an hour or more] before i can trust that the new results are reliable.

 

ok mick i have a bendix carb with a non adj.main jet.i just did the head gaskets and rocker gaskets.new bands on manifold.i live in nw.ind.it was in the 50's when this started happening and like i said never needed to be chocked. cool weather or hot,and never had this heavy sooting at the rear plug.they always burned that nice tan color.i know in the fac.book for the bendix carb it says to start at 11/2 to 2 turns on the idle mix screw then adj.from there.mine seems to be best at 2 to 21/2 turns.but like i said i really think it just needs a tune-up

 

I am not familiar with the Bendix. But if the recomendation is for 1,1/2 to 2, and you are at 2 to 2,1/2 then a larger slow jet would be indicated.

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noticed im getting spark behind the points plate where the weights are is that normal?i also noticed that the spark is a blueish yellow at the plugs.
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I hope someone else will comment on this.

 

yes so do i.also since this happened its harder to start.