Backfire Problem

[terpi]

Good day!

This is my first time to create a thread and hoping somebody can help me out with my problem. Here it goes.

I had installed 60mm bore, cam, stiffer valve spring and some headworks to my bike. The problem is it is now having back fire. I am using 4N big elbow exhaust and still have stock carb and jettings. I just had changed my spark plug earlier and replace new gasket in the exhaust connecting to the pipe.

What seems to be the problem here? Thanks a lot guys.

 

[latebloomer]

jettings?

 

[john_carlo]

Good day!

This is my first time to create a thread and hoping somebody can help me out with my problem. Here it goes.

I had installed 60mm bore, cam, stiffer valve spring and some headworks to my bike. The problem is it is now having back fire. I am using 4N big elbow exhaust and still have stock carb and jettings. I just had changed my spark plug earlier and replace new gasket in the exhaust connecting to the pipe.

What seems to be the problem here? Thanks a lot guys.

change your jetting 60mm bore in stock jetting is not compatible

 

[terpi]

@ latebloomer,

stock carb, did not change the jettings. Btw, am using AC engine.

@ john_carlo

what size do you recommend?

 

[terpi]

@ latebloomer,

stock carb, did not change the jettings. Btw, am using AC engine.

@ john_carlo

what size do you recommend?

 

[latebloomer]

there' s a thread regarding jettings applicable to bore upgrade pakisearch mo lang
maybe m not sure
115mj
25 pj feel free to correct mga masters

 

[terpi]

@late

i did some backread already but it is leading me to nowhere. I thought it might be more applicable to create a thread to isolate my case amongst other cases.

btw, sorry for the double posting. Am not sure what's happening seems like my internet connection is going crazy.

 

[latebloomer]

better ask /pm sir thopiang or admin for proper jettings
and u can order from sir admin

 

[terpi]

better ask /pm sir thopiang or admin for proper jettings
and u can order from sir admin

Thanks for the info bro.

 

[linjunvelasco]

sir try to change your carb to 28mm or 30mm believe me youll never experience any backfire again ( much batter kung open carb but with velocity cup )

 

[john_carlo]

http://www.yamahat135.com/threads/big-carb-jet-sizes-recommendations.2584/

try back reading this thread sir...

 

[Paladin]

@60mm bore use 125-38 jettings for 28mm keihin carb.

 

[terpi]

linjunvelasco and Paladin,

so it isn't really recommended to increase jet sizes using stock carb? Based from some thread ive read, am a bit apprehensive going for a bigger carb due to the difficulties in tuning them.

@JohnCarlo,

Thanks for sharing the link for me.

 

[john_carlo]

linjunvelasco and Paladin,

so it isn't really recommended to increase jet sizes using stock carb? Based from some thread ive read, am a bit apprehensive going for a bigger carb due to the difficulties in tuning them.

@JohnCarlo,

Thanks for sharing the link for me.

you can use stock carb but ported + jettings this is the one im using in a 57mm bore, stock looking but its a 26mm ported

 

[terpi]

you can use stock carb but ported + jettings this is the one im using in a 57mm bore, stock looking but its a 26mm ported

John,

did you block the AIS too? Does it have great effect addressing back fire issue?

 

[john_carlo]

John,

did you block the AIS too? Does it have great effect addressing back fire issue?

AIS is disable paps since im not using the stock pipe so no need for the AIS... even if your AIS is disable but your carb is not properly tune this cause for a backfire too

 

[chrisniper19]

AIS is disable paps since im not using the stock pipe so no need for the AIS... even if your AIS is disable but your carb is not properly tune this cause for a backfire too

prepare for all this stuff when i get back home im very excited about stock looking but 26mm... and dont know how to disable AIS...

 

[terpi]

AIS is disable paps since im not using the stock pipe so no need for the AIS... even if your AIS is disable but your carb is not properly tune this cause for a backfire too

Ah ic. it isn't really a guarantee that it will solve the issue. I guess i have no choice but to go for a bigger carb. Thank you

To All,

I will keep you guys posted. Thank you for helping out.

 

[terpi]

so.. i changed the carb's main jet from stock to 115. Unfortunately, it did not work. My bike still has back fire issue.

 

[Paladin]

so.. i changed the carb's main jet from stock to 115. Unfortunately, it did not work. My bike still has back fire issue.

Even if you change the jetting there will still be backfire. Theres a tubing that must be closed in the exhaust to eliminate the backfire.