Jump to content
Sign in to follow this  

XT350 hesitation and lean mixture woes - Fixed!

Recommended Posts

I thought I would put some words in here for those of you having issues with the dual YDLS carbs on XT350's. My bike was rebuilt by myself after purchasing it and finding out the cylinder and piston were way out of spec. Upon putting it all back together I noticed first off that when the bike reached 4K RPM it would start hesitating badly to the point of not being able to throttle through it. I then started my trek into the world of YDLS carbs and XT350's. I could not give up on this bike as I had way to much money in it to ever make it back.. this would be my bike for a long time. The next thing I noticed was that it seemed to be running lean and would pop and spit and run hot. I checked the plug and it seemed to be running lean with a white tip. I had not done anything with the carbs as the bike ran before the overhaul (plus a little impatient).

I started reading through ThumperTalk forums and began to realize this whole issue is a WELL known and documented one. Some of these posts went on for pages and pages with a lot of gain, but some never had a 100% solution. I took the carbs completely apart, the "slave" carb as I call it had been mucked with at some point in time and the main jet was cross threaded - THANKFULLY I had another set of carbs.. swapped the other slave carb onto the setup.. spent 3 hours thoroughly cleaning the jets and found them to be very clogged and dirty. I dropped the carb needles one notch on the slave side and 2 on the main carb. I set all the jets back to spec except for the air/fuel screw next to the float bowl - this I have out 4 to 5 turns. (better starting - proven!). I synced the carbs and checked the floats. I put the carbs back on and the bike ran great! It was now running richer at idle... BUT the hesitation moved from 4k RPM to 5k RPM... At this point it had been about a month and a half of summer (live in Ontario, Canada).. so it was getting to the end and I was getting a little ticked I couldn't ride the bike. I will not ride a bike that I do not know is running 100%, especially after spending money and time I cannot get back!

I pulled the bike out one day to go for a quick ride around the house. I took the bike out, started up on the 3rd kick... waiting for it get off choke... blahhhhhhh.... dead... no fire.. no spark.. nothing.. LIGHT BULB moment! I tested the stator, the source oil tested slightly out of spec and the pickup coil tested way out. Again.. thankfully I had another bottom end which had a stator and pickup in it... I tested it.. RIGHT ON SPEC! Wooohooo.. lucky day! I bought a flywheel puller and got down to business. I soon had removed the good one from the old bottom end and had it on my bike.

Another week went by and I finally had a chance to hook everything up and give 'er a shot. I primed it with a little gas down the spark plug hole, pulled the choke and kicked. It started!!! Unfortunately.. badly.. very badly! This is the moment where you think... ***!!!

I had a good thinking session that night and thought to myself.. what have I done to the carbs that would make this now run worse with the new stator. I remembered I had tried to mess with the timing of when the slave carb kicked in to see if it would help with the hesitation. The next morning I was up and at 'em early. I re-adjusted the timing to spec for the slave carb and fired it up... WOW... no spitting.. no popping... just glorious thumper noise! Now comes the moment of truth... do I take it down the road and risk having it hesitate again and thus ditching it and setting fire to it???? Or do I take the chance to have an excuse to drink a beer REALLY early? .... Mmmm.. Beer... I was off! 1st...... 2nd...... 3rd.... Right about here is where the hesitation was.... throttle through, NOW PIN IT! ROOOAAARRRRR.... 4th!.... then 5th..... THEN 6th..... OK BRAKE!!!!!!! :p - One happy banana... no hesitation at all!

I had a former friend of mine a while back ask about spark being the problem.. he said "What if it is getting to those RPM ranges and the spark is not enough to keep up or is not firing quite correctly?" I said... nawwww... couldn't be. Thankfully the lost friendship was not over this advice or I would look like a complete idiot! THE PICKUP AND/OR SOURCE COIL WAS THE PROBLEM! People... get out those testers and check the resistance... must be 10% give or take... anything out of that I would not deal with.

Pulser/Pickup Coil - B/W & Red - 221.0ohms +/- 10%

Source Coil - BR/Black - 444ohm +/- 10%

I was told at the shop that anything outside of those specs and they should be replaced.. no questions asked. If you are having the hesitation issues with your XT350 check these specs.....

Here is a video before I had the issue with the stator and stuff. I own this 1986 Yamaha XT350, a 1976 Honda XL350, a 1977 Yamaha DT400, a 1972 Kawasaki H1 500 2-Stroke Triple and last but not least... old faithful.. a 1983 Honda Big Red 200 Chain.

This is a hobby and passion of mine which started a long time ago. I am 30 years old and just started heavy into it over the last 3 years. I have owned a 1986 Kawasaki KX250, a 1979 Yamaha YZ250, a 1982 Yamaha YZ125, a Benelli Dynamo 60cc, a 1971 Yamaha JT1 (60cc), a 1983 Honda XL600 (still kick myself for selling this baby), and a 1989 Yamaha Moto-4 250 all within the last 3 years... wheel and deal... buy cheap, fix cheap and resell for profit. The only way to go! My wife doesn't mind unless I don't make money.. ahaha.. oh and I have a full time job as well as a Computer Technician (15 years).

That is enough for now... not the whole life story but should entertain some. I am looking for start a hard-to-find parts store online so please share some of those hard to find parts and I can locate them... I can find a needle in a haystack blindfolded. Trust me! :thumbsup:

I hope to get some talk going and chime in when I can in the forums. I am by no means an experienced motorcycle mechanic. I have the knack and the heart to completely rip apart something I have never seen before, fix it and put it back together. Just something that comes natural for me... but believe me.. I have ruined many things and thus learned A LOT of lessons along the way. The best lesson... research. A very smart friend of mine said.. if you find something you can't fix... get online.. someone else has been there and fixed that already. Work smarter... not harder!

Take Care....

Barfass...

  • Like 1

Share this post


Link to post
Share on other sites

Barfass,

Good story. Glad you got that XT working for you. I've owned 2 of these XT350's (my 2nd is up for sale now). Great bikes, and pretty simple to work on with a decent repair manual. Hope your parts search thing takes off.

Psycho

  • Like 1

Share this post


Link to post
Share on other sites

Great looking bike. I almost ran out to barn to make sure mine was still there.:thumbsup:

Check out my garage pix for some ideas to clean up that rear fender.

In the video that the spark arrester was missing. Is it, or am I just blind?

Share this post


Link to post
Share on other sites

Thanks Psycho18th for the comments.. I am very happy that it finally worked out. I was beginning to think I might have to give up but that is just not in my vocabulary.

jsnmid - Your bike was the inspiration for this bike. I am really glad you found the post and responded... thanks! It was about 2 or 3 years ago around Christmas time that I was bored and waiting for the cylinder and piston to arrive. I was on here having a look around and noticed your bike. I went and had a look at all the pictures... best looking XT I have ever seen... so I went to the local spray bomb dealer and got some paint and went to work. I should make a thread and post the pics of the rebuild... always something I have wanted to do. Any ways, hope you aren't miffed I stole the idea from you... consider it a complement because I love your bike.

As for the spark arrester I think everything is there... but possibly not as I have always wondered about the big exhaust that it has.. I know it is stock. I have been having some issues with white smoke out the tailpipe and I think it is just condensation getting in as I don't usually run the bike very long or never have because it has had issues until I fixed the stator... so... I got out the repair manual and it said to remove the screw from the back of the exhaust and pull out the inerds... well the screw is non-existent and the inerds would not pull out. You may be right... it may be missing... would this also make it run leaner? Now you have me second guessing myself about the exhaust but that is good... let me know.

Barfass

Share this post


Link to post
Share on other sites

Don't worry about stealing the idea from me. I stole it from someone else.:thumbsup:

It actually all started with the black YZ front fender I had laying around...

and winter. You obviously know how it goes.

I could only find 1 pic of what the back of the stock muffler is supposed to look like.

Not my bike, but at least it's the right color.:blah:

BritXT350.jpg

If you have a big hole, instead of the insert with a smaller hole, you are missing the spark arrestor.

This will cause the bike to be super lean.

I honestly don't know if it's possible to get the jetting right with a fully open exhaust. Even if you could, I wouldn't. It will kill the awesome bottom end the bike is known for. Opening up the exhaust only help up to a point. This bike needs at least a little back pressure to run right.

I think the insert is kind of expensive, but you may be able to find one on ebay.

Another option would be to fab something up yourself. I may be giving this a try soon since the spark arrester part of my insert is falling apart.

Share this post


Link to post
Share on other sites

FYI: Rattle can paint only lasts a couple of years on the trails. My bike is looking pretty rough. I think I might strip it down and freshen it up.

Share this post


Link to post
Share on other sites

jsnmid - Thanks for the clarification on the exhaust. I just sold my electronic drums so I have $400 sitting in my pocket. I will head to the Yamaha dealer down the way and order one. Bikebandit lists them as $100 and the dealer is usually pretty close to that or less. Thankfully they kept these bikes the same for MANY years. I would rather just have a new one and not take the chance off of e-bay. Plus at the moment there are only full exhausts for sale. My exhaust is very nice with no dents. This is the next step to getting this old girl back in shape.. I would rather put the money into it so I know what I have.

The rattle can paint started to come off when I was washing it the one day.. needless to say there will be another strip down in it's future. I also want to change all the bearings and bushings and finally unseize the rear axle shaft. Also rebuild the forks and new tires.

I have to say that even though a lot of money has been spent already it is really nice to be able to "know" your bike in and out completely... and that I sure do!

Share this post


Link to post
Share on other sites

If you want to look me up on that thing called "Facebook" :thumbsup:

Look for "Craig Hurlbut" - hence my username.. you figure it out!

I will put the XT350 as my profile photo for a couple of days... if you are not on Facebook ten I guess I will have to get the pics up here... also pics of all my other toys past and present on there.

Barfass...

Share this post


Link to post
Share on other sites
jsnmid - Thanks for the clarification on the exhaust. I just sold my electronic drums so I have $400 sitting in my pocket. I will head to the Yamaha dealer down the way and order one. Bikebandit lists them as $100 and the dealer is usually pretty close to that or less. Thankfully they kept these bikes the same for MANY years. I would rather just have a new one and not take the chance off of e-bay. Plus at the moment there are only full exhausts for sale. My exhaust is very nice with no dents. This is the next step to getting this old girl back in shape.. I would rather put the money into it so I know what I have.

The rattle can paint started to come off when I was washing it the one day.. needless to say there will be another strip down in it's future. I also want to change all the bearings and bushings and finally unseize the rear axle shaft. Also rebuild the forks and new tires.

I have to say that even though a lot of money has been spent already it is really nice to be able to "know" your bike in and out completely... and that I sure do!

Some notes on paint.

Get the tank professionally painted including clearcoat. I don't know of any rattlecan paint that will hold up to even a little gas. If you strip and prep the tank it should be pretty cheap.

Use Krylon Fesion plastic paint. The prep is very inportant here. You need to skuff the plastic up to take the shine off. Use many light coats and follow the directions as fare as time between coats nad total cure time. I had to do mine a few times before I was happpy.

I really wouldn't bother with painting the front fender. It's going to get beat up quickly. Order up an aftermarket black YZ front fender.

Share this post


Link to post
Share on other sites

thank you for the post!! you have just solved the problem i am having with mine. we just figured out before the riding season was over that i was having a spark problem on my moddded 2000 xt350. figured it out using an o2 sensor as i had it jetted ritch and made no difference. now i know whitch one i should be changing.

Share this post


Link to post
Share on other sites

Awesome! I am glad the post helped you out. I really think that this is one of the more common miss-diagnosed problem with the XT350's. What made me think of this in the first place was my old 1983 Honda XL600. When I bought it I was told it was the CDI, but the bike had spark.. just VERY weak. Called a friend and he immediately said "Stator.. if it is a stock stator, that is the problem" I guess these had a lot of issues with the stator which mimicked carb issues as well. I changed the stator with one from www.RMSTATOR.com and it fired right up and ran great.. no more issues. I think these XT's had a similar problem. Good Luck with the bike!

Share this post


Link to post
Share on other sites

I just started repainting my 93 xt 350 tank. The ugly Crockett and tubbs Miami vice stickers had to go. Oem stickers were clearcoated on the tank so I da'ed them off. I have filled a few dings and now she has been primed and painted base coat white. I found some red and black xt decals that I'll put on and clearcoat everything. I may put some red on the top of the tank around the fuel cap down to the seat. Already have more hours into it than I expected. Had to sand out a waterfall. I'll pOst some pics after it is done. Thanks for the fender tip. Did you just have to shim the aft side of the front fender to get it to fit? Any advice on Handlebars? Wouldlike to go to a 1 1/8 fatbar.

Share this post


Link to post
Share on other sites

Barfass, my bike has not been ran for a year. I just purchased it and did notice a bit of a flat spot @5k. Found the battery is toast and the gas was a year old so the fact that it started on the second kick and ran smoothly without backfiring was a good sign. Would the dead battery have anything to do with the flat spot in the power band or is that just the way the dual carb setup acts? Looked at your link and they only showed XT600 stators in stock. Can you call them and get others or did you get yours rewound? I have the bike torn down so I won't get a chance to ride it for a couple of weeks. ANy other mods I should do? What is the airbox mod I have been hearing about? I put in a new UNI filter already. Am changing the fluids including fork oil (15wt???) Anything else I should look at doing now would be appreciated.

Cleaver

Share this post


Link to post
Share on other sites

Glad to hear my post is helping out others... I figured I should share the knowledge so others don't lose their hair over it all! I just got mine about 95% completed with the help of another XT350 lover.. pretty much got the whole bike complete (less tank, carbs, head and rear wheel) in parts (everything bagged and tagged!) for $500. The bike only had 20,000kms on it and had an ownership with the frame as mine does not. I swapped everything over on Saturday to the new frame. I will post some pictures soon.

Share this post


Link to post
Share on other sites
Barfass, my bike has not been ran for a year. I just purchased it and did notice a bit of a flat spot @5k. Found the battery is toast and the gas was a year old so the fact that it started on the second kick and ran smoothly without backfiring was a good sign. Would the dead battery have anything to do with the flat spot in the power band or is that just the way the dual carb setup acts? Looked at your link and they only showed XT600 stators in stock. Can you call them and get others or did you get yours rewound? I have the bike torn down so I won't get a chance to ride it for a couple of weeks. ANy other mods I should do? What is the airbox mod I have been hearing about? I put in a new UNI filter already. Am changing the fluids including fork oil (15wt???) Anything else I should look at doing now would be appreciated.

Cleaver

Hey CleaverId, My bike did not have a battery hooked up when all of this was going on. In fact the bike had no power accessories at all except a UFO aftermarket headlight. Check your stator before messing with anything.. it is the easiest thing to check and it sounds like the carbs are OK (they could always have a cleaning) always do the easiest first. The RMStator link is more for the rewind option if they don't have an actual one in stock. The good thing about these stators is that the coils are replaceable and readily available new from a dealer $100 or so. The complete assembly is around $500. If you are handy with soldering and can find the same gauge wire as what was on it (has to be coated copper) then you can easily rewind them.. it is a little tedious but can save you a lot of coin! :excuseme:

I wouldn't do anything to your air box unless you want to get into re-jetting the carbs. These bikes are lean as it is and if you open the air box up (drill holes in the side) then you are going to be getting a lot more air which could result in a fried piston and possibly lower end damage, cylinder scoring and head damage. The same would go for an aftermarket exhaust.. they open up the exhaust so more air can flow and thus make it run leaner.

There is a company which sell on ebay jet kits for the XT350. You let them know what you have (any mods, air box, exhaust, etc) and they will ship you the correct jets for it. I DO NOT know if they work or what but their reviews seem to speak for themselves.

I am just diving into the realm of fork rebuilding so your guess is as good as mine on the weight of oil to use. I would say that sounds good though. I know for a lot of people it is a personal feel rather than "the book said to use this".

I will be posting pictures of the bike soon as I just redid it again with a new frame with ownership. Gonna be on the road and trails soon enough!

-10 outside tonight... eeckkkkk... :busted:

Share this post


Link to post
Share on other sites
Thanks for the fender tip. Did you just have to shim the aft side of the front fender to get it to fit? Any advice on Handlebars? Wouldlike to go to a 1 1/8 fatbar.

Just shim the back.

FWIW, I ran 15wt fork oil for a while and it was better than stock. Right now I'm using ATF with Progressive springs and that's working out pretty well also.

To be honest, any new fork oil should help. The grey snot I dump out of the forks each time I change the oil can't be working well. I may stick with the ATF because it's cheaper and seems to be working. It will be less painfull($) to change it out frequently.

Share this post


Link to post
Share on other sites

I read somewhere that the 15 wt helps a little with the fork dive. We'll see. I am also thinking about racetec emulators. My buddy that used to race and is big into riding told me to save my money on the pipe I was looking at and spend the $150 on emulators. He said it would be the best bang for the buck. (I'm looking at installing these on my 04 955 Triumph Tigger also)

BTW: You will need a tool to install the new fork seals and drive them in, I'm sure it can be made at home.

jsnmid, do you remember where you got the progressives from and how much they were?

The carbs were gone through a year ago and it seems he did a good job. Float levels are perfect and he richened it up a bit adjusting the needle I believe.

I am trying to locate your wiring to ring it out.:excuseme:

I think the source coil is off of the mag wiring harness at the control unit connector. "Source Coil - BR/Black - 444ohm +/- 10%"

The "Pulser/Pickup Coil - B/W & Red - 221.0ohms +/- 10%" I am having a hard time finding. The only black and white wiring on the print is to the engine stop switch. Are you referring to the regulator rectifer or is this also coming off the mag harness?

Going in to work though I'm off today to sand on the tank and pick up my Fluke meter. Hopefully my decals show up today so I can continue with the paint! Won't have a seat back for a week or so yet, getting it recovered and widened for comfort.

Doesn't matter anyway, 10deg F here today. A little too chilly.

Share this post


Link to post
Share on other sites

I got the springs for free so I can't help with the price.

They are XR200 springs from Progressive Suspension.

You have to make a new spacer, but I think a new set of springs has the instructions and materials needed.

I believe the Emulator you are talking about would also be for a XR200.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×