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Won't Start When Hot
- Thread starter sihnku
- Start date
Ed In Mississauga
Well-known member
Try starting it with the throttle wide open when it's hot... if it starts after several cranks, then its probably getting flooded... might have to get the carb floats adjusted.
an
My bike is currently doing the same thing... mine's an 83 V45 Sabre and the carbs are an absolute PIA to remove and put back, so I've been too lazy to pull em out.
an
My bike is currently doing the same thing... mine's an 83 V45 Sabre and the carbs are an absolute PIA to remove and put back, so I've been too lazy to pull em out.
cbr_rr
Active member
I have a 2004 zx6rr that doesn't start as well when its hot as it does cold. Cold it will fire right away when cranking. When it is hot, it cranks for much longer and when it does fire it does so slowly and doesn't sound happy. The bike runs fine otherwise.
If I open the throttle even a little bit it fires right away. The bike is fuel injected. Any advice?
If I open the throttle even a little bit it fires right away. The bike is fuel injected. Any advice?
theraymondguy
Well-known member
Valve lash adjustment is critical in performance engines. As time marches on, the intake and exhaust valves will wear into the seat. This can cause the lash (space between) the valves and the lifter to close up, potentially even causing the valves to be held open.
This results in a drop in compression, not a total loss, but a drop. The engine will spin 250-400 rpm on the starter; at idle the bike will run about 1200-1500 rpm. The difference in engine speed between the starter and normal idle can be enough to mask the loss in compression.
Generally speaking, valve adjustments are done in 5-15000 KM intervals; however, check your manual - could be more or less.
Those of you who have "shim under bucket" valves can expect to pay a little more for the adjustment, vs. those who have a traditional tappet type, as there is a little more labour involved and at least a couple of shims. This is delicate work, not for the faint of heart.
As seen above, the beginning stages of a shim under bucket valve adjustment on a customers' KZ550. This bike came in hard start, full on choke or no hope and sputtering. Left starting with the choke full off and running like a champ with over 64000 on the dial.
This results in a drop in compression, not a total loss, but a drop. The engine will spin 250-400 rpm on the starter; at idle the bike will run about 1200-1500 rpm. The difference in engine speed between the starter and normal idle can be enough to mask the loss in compression.
Generally speaking, valve adjustments are done in 5-15000 KM intervals; however, check your manual - could be more or less.
Those of you who have "shim under bucket" valves can expect to pay a little more for the adjustment, vs. those who have a traditional tappet type, as there is a little more labour involved and at least a couple of shims. This is delicate work, not for the faint of heart.
As seen above, the beginning stages of a shim under bucket valve adjustment on a customers' KZ550. This bike came in hard start, full on choke or no hope and sputtering. Left starting with the choke full off and running like a champ with over 64000 on the dial.
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Try a new battery. Sounds stupid, but I had the same issue and when I changed the battery all was good. No kidding.
Not necessarily. On a cold start, the ECU will crack open the throttle and/or allow a bit more air in through the IACV to prepare the engine for fast idle after it fires up. Also, the valves are made of steel and the cylinder head is made of aluminum, and the difference in thermal expansion rates can affect the valve clearance a wee tiny bit - and if it's on the hairy edge, that wee tiny bit might just be enough to make a difference.
For the moment, see if cracking the throttle open a wee bit by hand gets it going when hot.
It's possible. Sometimes, cranking a hot engine can require more power than cranking a cool (note: "Cool" - not "Freezing cold") engine.
The other thing is that if the engine is not stock in any way (exhaust system? intake flapper valves?) the change could have affected the amount of fuel the engine wants during cranking, and the stock fuel delivery might be giving it a little too much. Again, crack the throttle open a little, it should start if this is the case.
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