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1997 Yamaha xt350 running lean

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Hi all, first post. Great site!!!

I have little motorcycle knowledge but tons of car knowledge. I read up on motorcycle carburetors and I think I have it down. here's the question(s).

This is a brand new carburetor with stock jetting and it seems to be running lean at idle and through part throddle. When I got it back from the shop (who put the carb on) it would barly keep an idle at 1800 rpm and even stall sometimes. If you gradually started to give it gas it would studder and pop. Sounds like typical lean scenario.

Question 1) I go to see how far out the fuel screw is turned out and it is three turns. Seems really far but it is running lean. I give it about 3 more turns out (now at 6 turns) and it runs GREAT at idle. I can even get it to keep an idle at 1200 RPM (could never do that before). So why would a stock carb have such a lean pilot jet? That is at least what I assume this problem is.

Question 2) Now that is is running good at idle, before at part throddle it would studder pretty hard but now it only does it slightly. Would that mean the needle jet is also running lean?

Question 3) Like I said, I'm new at this. Can someone recommend a web site where I can get a jetting kit for a 1997 Yamaha XT350 non-california?

Thanks for all your help,

Scott

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Scott

What carborator does that model use? What you are descibing sounds like a plugged or way too small pilot. If it where mine I would drop the pilot out, don't go blasting it with compressed air, that may clear it but then we will not know what was going on!!

1: Hold it to the light and see if it was clear, If not blow very lightly to remove gas and look again if clear we need bigger! If blurry blow hard, if now clear we have water in the gas. Re-install and toss an once of rubbing alcohol into the gas tank, this will break the surface tension of the water and it will pass thru rather than plug the pilot;

(notes:

A) the pilot is the only jet in the carb small enough for water to plug, and

😢 Water in the gas is common with bike with steel tanks, they develop condensation above the gas level, should be stored with the tank full.

Next is still plugged it may need to soak in lacquer thinner to break down varnish or it may have a solid piece of debris in it, use a single bristle from a wire brush (techincally this is a no no as it will make the jet slightly bigger, in this case I am confident that it is boarderline too small anyway).

If you want to just buy a new jet lets just go up one size.

Next is the issue of the idle mixture adjustment.

If your carb has the idle mixture screw on the engine side of the main jet or center of the carb it is adjusting fuel, thus out is rich as you beleive it is based on your comments above.

However if your carb has the idle mixture screw on the air filter side of the main jet or center of the carb it is adjusting air, thus out is lean converse to your belief.

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Scott

What carborator does that model use? What you are descibing sounds like a plugged or way too small pilot. If it where mine I would drop the pilot out, don't go blasting it with compressed air, that may clear it but then we will not know what was going on!!

1: Hold it to the light and see if it was clear, If not blow very lightly to remove gas and look again if clear we need bigger! If blurry blow hard, if now clear we have water in the gas. Re-install and toss an once of rubbing alcohol into the gas tank, this will break the surface tension of the water and it will pass thru rather than plug the pilot;

(notes:

A) the pilot is the only jet in the carb small enough for water to plug, and

😢 Water in the gas is common with bike with steel tanks, they develop condensation above the gas level, should be stored with the tank full.

Next is still plugged it may need to soak in lacquer thinner to break down varnish or it may have a solid piece of debris in it, use a single bristle from a wire brush (techincally this is a no no as it will make the jet slightly bigger, in this case I am confident that it is boarderline too small anyway).

If you want to just buy a new jet lets just go up one size.

Next is the issue of the idle mixture adjustment.

If your carb has the idle mixture screw on the engine side of the main jet or center of the carb it is adjusting fuel, thus out is rich as you beleive it is based on your comments above.

However if your carb has the idle mixture screw on the air filter side of the main jet or center of the carb it is adjusting air, thus out is lean converse to your belief.

Hi and thanks for your reply. The carburetor is brand new and I had the tank flushed so I don't believe it is clogged or has water in the fuel. I guess anything is possible though. The carb is a Teikei Y24PV.

The mixture screw is on the engine side near the float bowl so I'm positive that it is a fuel screw not an air screw.

Don't know if this helps diagnose the problem but after it is warmed up if I leave the choke out about 1/4, it doesn't studder or pop at all; runs great!

Where do I get a jetting kit for the bike?

Scott

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A tank flush can sometimes loosen up rust that takes a while to finish coming out, so that is a possible issue, but more likely its just too small of a pilot. With it running that badly I wouldn't hesitate to go up at least 2 sizes, be prepared to turn the mixture screw back in a bunch. Check to make sure the float level isn't way off too.

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I use to have a 96 XT350. I made this web site for it.

http://www.imbris.net/~toadie/

After experiencing numerous downfalls of the bike I decided to sell it and buy a real dirt bike. Don't get me wrong it is a great bike for what it is built for, dirt road and occasional trip to town.

They don't make any jets for it other than stock. I had to buy a few stock ones and drill them out to a bigger size. The jets from an older XT600 will also work but I can't remember what size it is. Another thing to check is the secondary carb timing. If it opens too early it will be lean and pop and the bike will die.

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Stupid question. How do I find out what my pilot and needle jet #s are and what the #s are for 1 or 2 bigger?

Thanks, Scott

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This runs better at partial choke until warm it classic ooooh toooo lean idle circut. I have never met that carb, bet the shops are going to have zero jets for it.

If it where mine I would go to an industrial supply tool store, not sears, buy a set of drills that run from a #60 to #80 (this is tiny stuff) and a mini chuck that will adapt your drill motor to those drills. Then take the pilot jet out, find what size fits, it will probubly be in the 70's (high numbers are smaller), in iches something in the range of .014"??? Then I would drill it out bigger. If the next size is less than .002" jump one size past it. You will be suprised how much better the bike will be and I bet you don't spend $25

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