Motor runs for a second then dies

With good cold compression and valve clearances within specs, would suspect dry spark plugs to result from imperfect choke (enrichener) circuit and/or imperfect pilot circuit in the related carb. Or too low fuel level for whatever reason.

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I adjusted all of the float levels using the clear tube method, turned the four air screws all of the way in, left the two throttle cables disconnected, and turned the choke all of the up. After kicking a couple of times the engine sputtered a couple of times. After checking the plugs they are still dry. The inside of the carbs is spotless. The engine acted like it really wanted to run, but it just didn't.

If the air screws are turned all the way in, try backing them out about 1 + 1/4 turns and try to start it again. Ed

AnthonyKiser1977 wrote:

I adjusted all of the float levels using the clear tube method, turned the four air screws all of the way in, left the two throttle cables disconnected, and turned the choke all of the up. After kicking a couple of times the engine sputtered a couple of times. After checking the plugs they are still dry. The inside of the carbs is spotless. The engine acted like it really wanted to run, but it just didn't.

OK, as ed said, the air screws are required to be open, at least 1/2 turn. Best at 1 - 1+1/2 "usually".

Is the "air screws" located closest to the engine side of the carb, or the air box side? If engine side - its a mixture screw, so unscrewing it adds fuel mixture. if air box side, then it is an air screw, so screwing out adds more air to pilot mixture.

What size pilots are in the carbs? Origional?
Have you made changes to exhaust/filtration?

Has a compression test been performed?
If engine has too low compression on 1 cylinder, and sync is not good, engine may not run after momentarily starting.

They are the brass screws located towards the outside of the carb (legs). The only mods that the bike has are pod air filters, dyna green coils, and dyna plug wires. There is the jet by the float and the jet with the needle seat. What numbers should they have on them?

AnthonyKiser1977 wrote:

They are the brass screws located towards the outside of the carb (legs). The only mods that the bike has are pod air filters, dyna green coils, and dyna plug wires. There is the jet by the float and the jet with the needle seat. What numbers should they have on them?

Imo, needle jets are inconsequential relative to the issue at hand.

Could try using some starter fluid sprayed through carbs.

If runs on the starter fluid, that's evidence of pilot circuit being clogged. Especially given good compression, valve clearances within specs, and proper float bowl fuel level, but dry plugs.

With proper fuel level, fuel/air mixture through pilot jet goes into carb throat and then sucked into combustion chamber.

Perhaps orifice at bottom of carb throat is clogged.

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Any possibility of bad fuel entering carbs, such as water or moisture inside the fuel tank or petcock.

Has petcock sediment bowl been cleaned?


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Am back to wondering about possibility of air leak.

Could be from items such as:

Loose clamp onto carb holder;

Damaged or worn out carb holder;

Carbs not properly fully and fitted into carb holders;

Leaking vacuum caps;

Leaking emission lines or fixtures, if so fitted.

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Have carbs been properly bench synced?

Thinking perhaps throttle slides were set too high during bench sync.

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Thanks for all the help, I now have more things to check tomorrow.

Earlier this evening I fully seated and then turned the air screws out 1 and 1/2 turns and sprayed starting fluid into the carbs. I then kicked the engine over a few times with the choke fully on, there was no noticable difference. Tomorrow I'm going to order a set of cam end seals from Z1 and check the valve clearances. While I'm waiting on the cam seals I will bench sync the carb slides, since they all don't look equal.