Raptor Forum banner
1 - 20 of 35 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter · #1 ·
I recently did the following modifications, Yoshimura full exhaust, Pro-flow air filter, holes in air box, Wiseco 11.1 piston ,port and polish head and Jetting 150 left 155 right.
The problem is gearing down or quickly releasing throttle when load on motor develops a backfire. Any suggestion.
 

·
Registered
Joined
·
827 Posts
join the club ive been trying to get my popping and backfiring problems to cease. good luck
 

·
Registered
Joined
·
2,786 Posts
throw 25 pilots in... backfiring (as you do described) is usually caused by a lean pilot circuit. Check your plug to be sure you have the right color. The Carb 101 sticky is very useful.
 

·
Super Moderator
Joined
·
17,062 Posts
Yes, you're too lean on your mikuni mains unless you're at a very high elevation. Even with a full airbox lid you need more fuel up top than that.

Try closer to 165/170, could need even more but it's a good starting point.
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #6 ·
Thanks guys for the prompt replies. I took all suggestions and went to work. First task, checked valve clearance, (too tight) adjusted intake 0.13mm exhaust 0.15mm.
Went a step up on mains 155 -160 ,adjusted needle to the third setting and also went one step in pilots (25) .Still experiencing popping at times put I’m determined to cease the problem. At this point I noticed gains in throttle response and power.
I been hearing positive feedback on dynojet needles, if I applied this step would I see positive gains?
:thumbsup:
 

·
Registered
Joined
·
9 Posts
Discussion Starter · #8 ·
Pilot’s screws left 3 turns, right 2 turns(stock settings) I will increase the mains 160-165. Thanks again.
 

·
Registered
Joined
·
2,786 Posts
lol, I chuckle every time i see your avatar, Papis.
 

·
Registered
Joined
·
1,027 Posts
I have this same popping when I let off the gas.

1000ft asl
25 polits
150, 155 MIKUNI Jets
Clips at 4th position

Full exhaust with open air box
 

·
Registered
Joined
·
1,027 Posts
I don't know what kind of needles came with the kit. What makes you think I need to change them to dynojet or gytr? Anywhere I can buy just the needles?
 

·
I am unique
Joined
·
22,621 Posts
the stock needle just can't flow enough fuel when you start modding like you did, I played with what you have years ago and when I changed needles the bike just worked better and was easier to jet
 

·
I am unique
Joined
·
22,621 Posts
ShawnTRD said:
I don't know what kind of needles came with the kit. What makes you think I need to change them to dynojet or gytr? Anywhere I can buy just the needles?
Just remembered I got some needles, I dont have the carbs anymore so I dont need the needles, Dynojet needles.
 
G

·
I thought backfire was running too rich no lean. I pop and backfire when i let off the throttle when i was hauling ass at high RPMs.
 
1 - 20 of 35 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top