Honda Motorcycles - FireBlades.org banner

1 - 16 of 16 Posts

·
Registered
Joined
·
86 Posts
Discussion Starter #1
So my 1993 cbr 900rr when cold pops and backfires blue flames! Cool to see but can someone tell me what is causing this and how to fix it. Also at about 6000rpm, it kinda boggs but it seems that you can power through it. Are these related?
 

·
Registered
Joined
·
342 Posts
we are talking when its sitting in neutral right?
my 96 will spit flames if its revved while its cold with the choke on. pretty much normal for cold carburated bikes.

now, with the bogging, if its doing that in neutral while your revving, its probably because your fouling out your plugs by revving under no load.

if this is while your riding, it depends on the bog type. the 900RRs midrange lag is right around there so it wont acellerate as fast... if its obviously bogging then you have somthing going on... probably in the carbs or induction(modded airboxes sound familiar). excessivevalve lash is also possible if its up there in miles but not likly
 

·
Registered
Joined
·
86 Posts
Discussion Starter #3
the blue flames are while its warming up at about half choke. the bogging is while riding, and a buddy said to have the carbs cleaned and sinked? the odometer has 22000+, but speedo doesnt work (on its way, gotta love ebay). Hey thanks so much for your reply, was starting to think my questions were dumn. lol
 

·
Registered
Joined
·
342 Posts
the blue flames are while its warming up at about half choke. the bogging is while riding, and a buddy said to have the carbs cleaned and sinked? the odometer has 22000+, but speedo doesnt work (on its way, gotta love ebay). Hey thanks so much for your reply, was starting to think my questions were dumn. lol
sometimes it takes a while to get a response around here... I dont know why.
it sounds like your buddy is right. they jsut need to be synchronized.. at 22k, if you dont know if the valve lash has been reset i would look into getting that done(or if your good with your hands, do it yourself and save some green:thumb:). excessive valve lash wont cause that but it defiantly wont help things...
 

·
Registered
Joined
·
86 Posts
Discussion Starter #6
Thanks again! You have any idea how much it costs to get all that done (valve adjustment and carbs syncronized)?
 

·
Registered
Joined
·
8 Posts
Hi Guys,

I've just replied to another posting with a similar problem.

The flames and popping are unspent fuel burning in the exhaust, obviously the purpose of the choke is to over fuel to let the engine run when cold and not have all the fuel charge condensating and being lost before the cylinder. Although it's essentially an over fuel device you could be getting too much fuel right through the revs. On and off the choke.

If it's bogging down, it could be the same thing off the choke. Over fuelling.

Good luck
 

·
Registered
Joined
·
86 Posts
Discussion Starter #9
I rescued the bike from a kid trying to make it a streetfighter/stuntbike, why you would want to do that to such a great bike is beyond me! He had shortend the Vance and Hines slip on and taken out the baffles for going to 12 o clock and other "nifty tricks". He did a clean job but between that and the Two Brothers header its sounds almost too GP.
 

·
Registered
Joined
·
824 Posts
ya the popping is caused by the air expanding rapidly in the exhaust pipe..and the flames are just a byproduct of unburnt fuel combusting from the excessive heat within the exhaust..they usually are seen together and really wont hurt the bike too much...the worst case scenario is that there is excessive fuel being dumped in to the cylinders by the carb and carbon deposits can accumulate on the plugs and inside the cylinders and ports and cause the engine to run like ****...this happens over an extended period though and would need to be pretty rich...
 

·
Registered
Joined
·
342 Posts
ya the popping is caused by the air expanding rapidly in the exhaust pipe..and the flames are just a byproduct of unburnt fuel combusting from the excessive heat within the exhaust..they usually are seen together and really wont hurt the bike too much...the worst case scenario is that there is excessive fuel being dumped in to the cylinders by the carb and carbon deposits can accumulate on the plugs and inside the cylinders and ports and cause the engine to run like ****...this happens over an extended period though and would need to be pretty rich...
carbon can build up rather quickly. ive seen it happen in a matter of a half hour (riding with the choke still on/ bad fuel) on the road and a matter of seconds by revving under no load..

best way to clear the buildup out of the head is to ride in the rain. as stupid as that sounds.. the moist air creates stam witch attacks the carbon. if your trying to get it out of an exhaust, Windex is about the best stuff out there for that
 

·
Registered
Joined
·
824 Posts
rain??? really! never knew that...i would think the conditions would have to be pretty bad though for it to build up that fast...
 

·
Registered
Joined
·
86 Posts
Discussion Starter #13
Wow!! All good things to had to my cbr's honey do list! LOL. I'm in washington state so i've been riding in the rain alot. A matter a fact it ran last night on my way home the best it has ever!
 

·
Registered
Joined
·
342 Posts
rain??? really! never knew that...i would think the conditions would have to be pretty bad though for it to build up that fast...
yep just plain old riding in therain. a buddy of mine (who also works on bikes alot) told me that one. it seems very unlikly but it does make a difference.. his other method for removing carbon is using a dropper and just dripping water drop by drop into each carb one by one with the bike in neutral and the airbox off (for a bike that uses an actual gas tank like the 900rr you need to rig up a external test tank for it to work). im weird and actually enjoy the occasional sprinkle while im riding so i usually just head out on a misty day insted.. now needless to say, you ahve to ride the bike for a bit after doing this to ensure all the water is gone...
 

·
Registered
Joined
·
86 Posts
Discussion Starter #15
I was alittle afraid to ride the 900rr on dry pavement, being it is much bigger then my 600 Katana. But now I ride rain or shine, mostly rain around here. lol
 
1 - 16 of 16 Posts
Top