[**DONOTDELETE**]

The bike has been running a little lean since I got it, which led me to replace the plugs since there was loss of power; the plugs were totally shot.

After the plugs were changed I rode it for 2 days, without a problem, and then it just started backfiring.

The bike runs great until it is warmed up. Once it is warmed up it runs with a little less power and once I open the throttle it will backfire.

Hope that helped.

 

[mcgsxr]

Does the bike have an airbox or pod filters? Do you know what size main jets are in the carbs?

Sounds like it is running more than a little lean - I had an 85 750 that ran lean and would shoot flames out the exhaust... That bike had a Hindle 4-1, UNI filters and 127.5 mains - I eventually went up to 132 mains, and it cured the problem.

Mark

 

[somejeffguy]

what did the plugs look like? it actually sounds like you're running rich....at least, that's usually what a bike running worse when warm than cold indicates. could be some extra fuel ending up in the exhaust and then being ignited, leading to the flames....

running lean usually doesn't cause damage to the plugs unless it's running so lean that the plugs get damaged by the heat.....whereas if you're running rich, you'd be prone to fouling the plugs and thus requiring their replacement.


also, check to make sure you don't have any vacuum or exhaust leaks, they could cause popping from the exhaust as well....

 

[**DONOTDELETE**]

My bike has an airbox (i believe) with a K&N filter on it, also it has a Yosh pipe. dont know how the jets are set up.

When I took the plugs out they were WHITE; totally burned up!

Thanks!

 

[**DONOTDELETE**]

Hello all.
I have an '89 750 and when the bike gets warmed up and I rev the engine the bike will backfire and flames come out of the engine!

It happens almost every time I go full throttle on the bike.

Any ideas?

Thanks!
-CarKnee

 

[gsxr1198]

Could be any of a number of causes from very simple (carb adjustment) to fairly complex (cam timing)...

Can you give us more to go by? ...did this just start? did you make any recent changes, or have another event like a missed shift? does the bike run well otherwise, or is it down on power?

Ed

 

[terryd123]

WAAY too lean if they are that white...stop riding that thing until you up your jet size..you'll fry the pistons....see what size mains you have and go up to increments on the main jet...do a plug reading after a hot run....the plugs should be lite golden brownish...with a hint of cinnamon....