4 stroke dirt bike question

[MPS]

I bought an old 85 XR a little while ago for a starter dirt bike. I have been wrenching on it lately...new sprockets, chain, shift lever, tire, and an Edlebrock carb.

I started it up today and rode it....after getting the carb in. I had this problem before I put the new carb in, but it is worse now... it sputters and backfires when I get into the top end.

I don't know much about dirt bikes, especially 4 strokes. Is there a jetting issue here? I tried to pull the spark plug out to see what it looked like, but I don't have the right millimeter size socket. Have to buy one tomorrow.

I played with the choke and that didn't seem to do anything.

Any ideas?

 

[Supplicate]

XR600?
I had a similiar problem with my old XR, it would sputter and fall on its face at high RPM, wound up being scary lean. Rallied the hell out of a pair of 600's till I stepped up to a 650R.

 

[FriscoProx]

I would bet the main jet in the new carb is for somewhere near sea level and your super rich because of the elevation. Not sure how to change the Edelbrock's main jet but would assume its similar to Mikunis or keihins on other sled and bikes. Check with your nearest Honda dealer and see what jet they recommend.

 

[MPS]

XR600?
I had a similiar problem with my old XR, it would sputter and fall on its face at high RPM, wound up being scary lean. Rallied the hell out of a pair of 600's till I stepped up to a 650R.

no its 350....wish it was a 600. I was thinking it was lean....what did you do to fix it? jets?


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[MPS]

I would bet the main jet in the new carb is for somewhere near sea level and your super rich because of the elevation. Not sure how to change the Edelbrock's main jet but would assume its similar to Mikunis or keihins on other sled and bikes. Check with your nearest Honda dealer and see what jet they recommend.

Well I got the carb from another snowester....he lives about 120 miles away from me, so the elevation isn't too different. Well I don't actually know he used the carb there....maybe it is jetted for sea level.

 

[Supplicate]

Yeah, my 600 was cured with jets. The 650 was made better with jets but really woke up with the Edlebrock Quicksilver pumper.

Is your Eddy a Quicksilver? If that is the model you have its most likely the wrong needle taper, had to run the middle needle (can't remember the number anymore, its been a few years ago) in Wyoming so I could stay in the middle of the adjustment range on it. No such thing as changing jets on the quicksilver, you just reach up under your tank and change the needle position a few clicks and you're re-jetted.

 

[spring snow hero]

does your 350 run dual carbs? if so the the plastic link between them can get out of phase and cause probs. if it is a single carb, try it with the choke on and see what up.............better or worse. also look at the cdi and be sure all wires are good. since you will have the tank off to do that, take the 5 minutes to check he valve clearances......forget what they are for that, but I would guess in the 6 on the ins and 12 on the ext. that should get you closer.

 

[montanasledder]

my xr 400 ran weird the the valves were out of adjustment

 

[Supplicate]

does your 350 run dual carbs?

Forgot about those. If it is does have the dual carbs, definitely check and make sure everything is working properly between them.

 

[adrenaline junkey]

mps the carb was ran here and also up at 9000 ft never had any issues with it. it was on an xr 400. you might not have enough adjustment in the external needle adjuster. remember its a pumper carb and may be giving you too much of a shot when your at full throttle , If anything I would bet your running too rich. Like you said tho get the plug out and see what it looks like.
take a look at the tuning guide http://www.edelbrock.com/automotive_new/misc/tech_center/install/off-road_carbs/Off-Road_install.pdf

 

[MPS]

mps the carb was ran here and also up at 9000 ft never had any issues with it. it was on an xr 400. you might not have enough adjustment in the external needle adjuster. remember its a pumper carb and may be giving you too much of a shot when your at full throttle , If anything I would bet your running too rich. Like you said tho get the plug out and see what it looks like.
take a look at the tuning guide http://www.edelbrock.com/automotive_new/misc/tech_center/install/off-road_carbs/Off-Road_install.pdf

Thanks for the tuning guide bro....yes A.J. is the good man I got the carb from.

To answer your question Supplicate....I only have one carb and it is a Qwiksilver II.

Spring snow...I tried the choke last night and it just killed it...so worse.

Do you all think I need to clean it? It looked pretty clean when I got it from A.J.....so I didn't worry about it.


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[MPS]

Ok just went for a ride with the seat off so I could adjust it as I rode....it seems to do better when I lean it, but still sputters and coughs. I'm thinking I need to clean the carb.



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[adrenaline junkey]

Ok just went for a ride with the seat off so I could adjust it as I rode....it seems to do better when I lean it, but still sputters and coughs. I'm thinking I need to clean the carb.


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Did you drill any holes in the air box? and i returned you pm

 

[MPS]

Did you drill any holes in the air box? and i returned you pm

ya....I drilled four 1 1/4 inch holes in the right side. i returned your pm back

Is there any chance this could be a coil or stator issue?


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[MPS]

Ok I had this bike into my mechanic and he put a new tire on for me....but he has never dealt with Eddy carbs before and he couldn't get it running better. I sent him the tuning guide and I don't think he read it. UUUGH

Anyway, I think it needs a lower numbered needle...so it leans it out at mid to open throttle. Where would I get a needle for this carb?

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