Backfire through carb????

[fishx65]

Did the topend on my 87 warrior about a year ago. Runs great but has a slight hesitation at high rpm. I've been getting a backfire through the carb every now and then while starting the motor. Any idea what causes a carb backfire? I have not done anything yet such as re-clean the carb or adjust the valves. Since I did a complete valve job, I know I need to get in there and readjust them.

 

['00 WO-YA!]

I'd start with the valve adjustment, it costs nothing but your time.

 

[jasonp]

Most of the time if the engine is cold and engine is ok and you are having this problem with sneezing out the carb, then the mixture is to lean. Most likely pops on decel. Turn the fuel screw out 1/4 turn.

 

[fishx65]

Just got up to my cabin and started taking her apart. The carb to cylinder head boot is falling apart. She was running a wee bit lean!!!!!!

 

[ryder133]

Yeah to lean is not good eh? I was going to call it flashback :/

 

['00 WO-YA!]

Damn boots!! I'm about to replace mine, pops on the high end, I temporarily put rtv over where the hole was & it slowed down the leak enough to majorly improve how it ran.

 

[fishx65]

Well, I've taken a good look at the joint and I'm trying to repair it myself. Cleaned it up really good, ran a thin bead of high temp RTV around the inside of the boot, reinstalled the aluminum joint and waiting for it to dry. After it dries, I'm gonna run a zip strip around the boot to really tighten things up. I see no reason why this won't make a nice durable repair but the local stealership down the road has one in stock if this doesn't work ($45.00!). Since I got her stripped down, I might as well check the valve clearence today. Ever since I did the topend, I've been hearing a high pitched chirping sound that's been driving me crazy so I'm thinking the carb joint repair might take care of this issue.

 

['00 WO-YA!]

Man, I gotta be straight with ya, rtv on the inside of that boot isn't gonna work out, the fuel is gonna break it down & the engine is gonna ingest it. Will it hurt it? Eh, prolly not, it'll likely strip off in a thin layer & the engine will just fart it out the exhaust, atleast as long as it don't hang up in the venturi of the carb.
I smeared my rtv around the outside of the boot just to experiment with slowing the leak down to make sure the boot was my primary issue, I have a boot in the mail.

 

[miami1]

$45 probley isnt to bad. the best deal on ebay isnt much better than that.

http://www.ebay.com/itm/Intake-Mani...Parts_Accessories&vxp=mtr&hash=item2c600b5830

 

['00 WO-YA!]

$45 is about what my local Yammy shop wanted. I just happened to work out a deal with Kyler when I bought the cam from him, he had a like new used stock boot so I gave hime $20 for it. It'll prolly outlast one of the ebay jobs!

 

[fishx65]

She's running perfect and the repair seems really solid. I thought of a few other options for this repair:

1. I'm gonna use a hose clamp instead of a zipstrip the next time I take it apart to clean the carb

2. If you take apart the old joint completely you will be left with the two aluminum pieces. I would think a short section of the right sized radiator hose and a couple hose clamps would make a solid repair.

 

['00 WO-YA!]

That same idea has crossed my mind. I could also tune the length of the intake runner shorter or longer with the hose. I might experiment with the idea a lil bit since I'll have the old boot to toy with. I'll Prolly even port the size a lil more & taper the aluminum to the rubber hose so the air doesn't beat against the ledge of the aluminum.

 

[fishx65]

That same idea has crossed my mind. I could also tune the length of the intake runner shorter or longer with the hose. I might experiment with the idea a lil bit since I'll have the old boot to toy with. I'll Prolly even port the size a lil more & taper the aluminum to the rubber hose so the air doesn't beat against the ledge of the aluminum.

I know exactly what you mean about tapering the aluminum for smooth flow. I was trying to think of a way to fill that 1/2 inch gap which will be left in the middle if using radiator hose. Maybe a chunk of smaller diameter hose or even a metal spacer would work. If my repair does not hold out I'm gonna give it a try.

 

['00 WO-YA!]

Just taper the aluminum man, you'll get the result you want & won't have to bother with any kind of spacer.