Backfiring through carburetor?

[Josh]

My bike has a intermittent back fire through the carb between idle and 1800 rpm, the problem is not noticeable at higher rpm's. I've been chasing this gremlin for a while and think I may have found the reason. Here is a photo of the right side intake manifold on my carbed Sport 1100. I circled the hairline crack with a pencil. The second picture is the outside of the manifold. I drew two arrows to indicate the point where the rubber boot clamps on to the manifold, thus covering the crack. So what do you guys think, could this be causing my problem? Does anybody have any recommendations for repairing a hairline crack in aluminum.

[mike wilson]

No pic, so it's a little difficult to say. It certainly sounds like an intermittent air leak could be the cause of your problem.

 

Generally, if you can't get it welded, a new part is needed. Sometimes you can use other methods, like epoxy, but it is often unsatisfactory in the end. A manifold should not be that expensive. Especially if you try Reboot Spares, who will have oodles of secondhand ones.....

[Guest Gary Cheek]

PM me I will reply with my address. Send the manifold up, I will weld it, re-machine if required and return it immediately. Should look like new.

[DeBenGuzzi]

PM me I will reply with my address. Send the manifold up, I will weld it, re-machine if required and return it immediately. Should look like new.

gary if anything goes wrong with my bike I will call you and do anything short of sleeping with you to get'er fixed, youre a stand up guzzsita if there ever was one.

[guzzijack]

Does anybody have any recommendations for repairing a hairline crack in aluminum.

 

Yes, Devcon F is what professional engine builders and machinists use for repairing casting damage

 

Devcon Website

 

GJ

[Josh]

My bike has a intermittent back fire through the carb between idle and 1800 rpm, the problem is not noticeable at higher rpm's. I've been chasing this gremlin for a while and think I may have found the reason. Here is a photo of the right side intake manifold on my carbed Sport 1100. I circled the hairline crack with a pencil. The second picture is the outside of the manifold. I drew two arrows to indicate the point where the rubber boot clamps on to the manifold, thus covering the crack. So what do you guys think, could this be causing my problem? Does anybody have any recommendations for repairing a hairline crack in aluminum.

[Steve G.]

A backfire is always indicitive of a lean burn. Causes can be wrong jets, leak or crack in the intake manifold, water in the fuel, etc.

Ciao, Steve

[Guest Mattress]

Loctite used to make a wicking anerobic sealant for weld and casting porosity. It was used a lot by new car dealers for filing casting flaws in auto trans castings. They probably still make it. It will flow into a crack by capillary action, expand and harden. A little heat seems to help.

 

The welding offer still stands. It is a far more positive, permanent repair than glues or fillers.

My 2006 Loctite catalog reccommends Fixmaster Aluminum Liquid or Putty for repairing parts. Liquid would wick more.

[Josh]

Loctite used to make a wicking anerobic sealant for weld and casting porosity. It was used a lot by new car dealers for filing casting flaws in auto trans castings. They probably still make it. It will flow into a crack by capillary action, expand and harden. A little heat seems to help.

 

The welding offer still stands. It is a far more positive, permanent repair than glues or fillers.

 

Thanks for the offer Gary. I've got a few things I'm going to try, if they don't pan out I'll contact you.

[dlaing]

That looks like a pretty small crack to me.

But I guess it could cause back firing

I am pretty sure it would not cause backfiring, unless also accompanied by symptoms of popping, especially durring deceleration. I believe a little soft popping is normal.(any opinions on deceleration popping???)

Glues might not do anything to keep the crack from growing, but glues are good for testing to see if welding will fix the backfiring.

Another test is to spray quick start on the crack while the engine is running to see if it effects the idle. But that is not always a conclusive test.

Note quickstart is bad for rubber and plastic and paint, etc. but it is good for cleaning out the crack before gluing

[Guest Gary Cheek]

Glue or any contaminate makes subsequent welding a bit more difficult.

When someting is cracked that shouldn't be I usually weld it or throw it out and replace it. Welding is easier and more positive than putties, pastes and glues that are usually used by amateurs.

[dlaing]

Thanks Gary, I figured wrongly the welding would have no trouble with the glue.

I really should invest in some welding gear and learn the skill. Lessons would not hurt, as I have not welded since the one time in High School shop class when I made a weather vane

Maybe I can make a Quat-D like muffler

[DeBenGuzzi]

Thanks Gary, I figured wrongly the welding would have no trouble with the glue.

I really should invest in some welding gear and learn the skill. Lessons would not hurt, as I have not welded since the one time in High School shop class when I made a weather vane

Maybe I can make a Quat-D like muffler

Learn nothing, they have welders now that are wire feeds and have charts right on the panel under the power setting that tells you where to spin the dials to and you can weld anything with them, I think they're like 3K for a base, don't quote me but my uncle is a pro welder and cert for every metal known to man, he says its idiot proof and can weld almost anything, he stopped using his heliarch and tig welder in favor of it, I assume if you have something tricky just need a different wire spooled through it.

[docc]

. . . he says its idiot proof . . .

 

 

Yes, yes, I'm mechanically inclined. I can screw up anything.