Author Topic: Buddies Pig is backfiring at high rpm... Too Rich?  (Read 526 times)

Offline MxM1980

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Buddies Pig is backfiring at high rpm... Too Rich?
« on: April 09, 2017, 05:24:18 AM »
Went riding with a friend yesterday... his machine ran great all day, that is up until the last hour or so... started backfiring and sounding like a shotgun going off when he would hit the throttle..... almost seemed like it was starving for gas... he could hold it at about 1/4 throttle as long as he wanted and it ran fine... but then he would "punch it" and it would bog and backfire like there wasn't enough gas in the bowl....if he let it sit and idle for a minute and gave the bowl time to refill, he could rev it no problem until the bowl drained and it started backfiring again..... So what I'm thinking is maybe the main jet is too rich and letting the bowl drain too quick? But then again it's only a 170 main and I've heard about people running a lot bigger than that.... we took apart the entire carb, made sure none of the jets were plugged and also checked needle valve to make sure it wasn't plugged... put fuel line in a bottle and opened the fuel valve and it seemed to be supplying enough gas... totally stumped... any help is greatly appreciated....
« Last Edit: April 09, 2017, 05:27:24 AM by MxM1980 »

Offline hsr-tm45s

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Re: Buddies Pig is backfiring at high rpm... Too Rich?
« Reply #1 on: April 09, 2017, 03:05:11 PM »
you did not say if you have done any other repairs, or do you ride is the mud or water? I would check the fuel tank vent hose first. good luck.

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Offline MxM1980

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Re: Buddies Pig is backfiring at high rpm... Too Rich?
« Reply #2 on: April 10, 2017, 03:45:16 AM »
Not really... it's a pretty stock bike.... he has a makeshift exhaust on it but it seems to work decent.... like I said we rode all day with no issues it was just the last hour or so.... but it happened to his first carburetor too (I sold him my stock carb when I went to an hsr45) we tried running it with no gas cap and it didn't make any difference...I'm wondering if maybe he's losing vacuum and his slide is dropping back down....

Offline hsr-tm45s

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Re: Buddies Pig is backfiring at high rpm... Too Rich?
« Reply #3 on: April 10, 2017, 07:43:57 AM »
Then check the fuel filter in the tank. What washe running on the on the fule tank selector ? Fuel or res.
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Offline Dirk1616

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Re: Buddies Pig is backfiring at high rpm... Too Rich?
« Reply #4 on: April 10, 2017, 10:34:37 AM »
Float! My buddies DS had float that wasn't adjusted correctly, and would do that exact thing, he would be fine in the lower RPMs, but in the higher ones, he would run out of gas, lose power, and would back fire real loud. You are running out of fuel in the carb bowl, and the float is not dropping soon enough to let more gas in. If you read OMR Carb Mods, it explains how to set the float correctly. You don't have to do the mods if you don't want to, that's up to you, I'd recommend them though, but the float information is still good to go by. I guarantee it's your float. Play with it some, while you have it apart, let the float down all the way, watch to see if the needle falls when the float does, if it doesn't, there is a tab on the float that pushes that needle up with 2 wires that come off of the needle to hug that float, bend those 2 needles to touch the tab of the float, it will make it a little tighter and help pull that needle down to let the fuel in. Hopefully that wasn't too confusing and helps you out!
2003 DS Baja         Riding at Bundy Hill and Silver Lake
Big Gun CDI, 11.5 JE Piston, Port/Polish, OMR Carb Mods,
Custom Mod End Cap, UNI Filter, More To Come?


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