GZ 250 Forums - View Single Post - Is my timing off? Bike won't run without choke and throttle

spldart · 09-29-2015, 10:22 PM

Raul is very near one of my thoughts.
Your choke and hold throttle symptom sounds like major vacuum leak / running lean.

Tightened your drive chain?
Messed with your timing chain?

Messing with the timing chain can cause serious engine run issues.
You must be sure the timing mark at the crank (viewable through that bolt portal) is where
it's suppossed to be in relation with the cam position.
BE SURE that you got it right as per service manual.

One last bit of advice that can rule out these two eventualities....

When bike is running and you hit the road and give it the beans (full throttle) ....
Does it go like it suppossed to or fall on it's face barely excelerating...
I'm talking about 4000 rpm. Not idle.

If it revs out and accelerates normally in the rev then your timing is fine and you got mixture
problems.
If the motor just wont give up any power even at the high rpm's then you may very well have
bunked your timing (valves to piston)

Lemme simplify.
Can the bike hit 50 or 60 mph without trouble?
Yes? Timing is prolly ok. Check mixture. Carb clog or intake leaks.
No? Check your timing again as per engine section of s.m. to be sure.

Vacuum leaks.
Little hose from carb to petcock.
Boot connecting carb to head.

Other issues requiring to much choke or throttle or both.
Clogged pilot circuit (you did just work on the bike... Some rust in tank found its way to carb bowl?)

09-29-2015, 10:22 PM	#8
spldart Senior Member Join Date: May 2015 Location: Stafford, Texas Posts: 604	Raul is very near one of my thoughts. Your choke and hold throttle symptom sounds like major vacuum leak / running lean. Tightened your drive chain? Messed with your timing chain? Messing with the timing chain can cause serious engine run issues. You must be sure the timing mark at the crank (viewable through that bolt portal) is where it's suppossed to be in relation with the cam position. BE SURE that you got it right as per service manual. One last bit of advice that can rule out these two eventualities.... When bike is running and you hit the road and give it the beans (full throttle) .... Does it go like it suppossed to or fall on it's face barely excelerating... I'm talking about 4000 rpm. Not idle. If it revs out and accelerates normally in the rev then your timing is fine and you got mixture problems. If the motor just wont give up any power even at the high rpm's then you may very well have bunked your timing (valves to piston) Lemme simplify. Can the bike hit 50 or 60 mph without trouble? Yes? Timing is prolly ok. Check mixture. Carb clog or intake leaks. No? Check your timing again as per engine section of s.m. to be sure. Vacuum leaks. Little hose from carb to petcock. Boot connecting carb to head. Other issues requiring to much choke or throttle or both. Clogged pilot circuit (you did just work on the bike... Some rust in tank found its way to carb bowl?) Last edited by spldart; 09-29-2015 at 10:35 PM.
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