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Top End job on XT350

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Hello everybody. I am new to this forum. This is my first post. I recently purchase a 1989 XT350 for $400. Appearance wise it looks really good, with the exception of a rusty chain and rip in the seat. No dents or broken plastics. Everything is there except the rear turn signals. It was in non-running condition when I bought it. (I should know better, but the price seemed too good to pass up). The guy told me it needed carb work was all. When I went to pick it up, he handed me the carb torn apart in a box, ha ha! Not really what I was expecting. I got the carb cleaned and put back together and on the bike. Of course the intake manifold boots were in bad shape with some cracks. I tried fabricating my own from some hose like some have done on here, but I couldn't get them to stay on. I ended up wrapping the old boots in several layers of electrical tape and putting them back on. I know...that will never hold for long, but I just want to see if I could even get the bike to start and I don't want to cough up $130 (sooooo ridiculous!) for two new boots at this point. I dumped the oil out of the bike. It was like black sludge with clumps and some crystal like chunks in it - that can't be good. There wasn't much oil in it either. I put fresh oil in it and cleaned out the filter. The filter had a little bit of metallic particles on it, but I don't know if it would be enough to cause concern. The filter screen had a rip in it, so I need to get that replaced. Now the bad part...after dumping out the old gas and putting in some fresh, I kicked it a few times and it fired up. I was excited for a few seconds until I looked behind me and saw the biggest cloud of blue smoke rolling out that I have ever seen! It polluted my whole neighborhood in a matter of a minute or two! Other than the smoke the engine ran good and sounded good. I didn't hear or feel any bad noises or vibrations. So, I am assuming, with that much smoke, that the rings are shot??? Would that be the general consensus? I would like some advise from you guys if you think it is worth putting money into it? Would a new top end most likely be all it needs? I have not done that on a motorcycle before, but I have on a car. Should I get it done by a professional and how much do you think they would charge? I see top end kits for $150. I wouldn't mind trying it myself, but I guess my biggest fear is something else being wrong, like bottom end or transmission. I did rid it around my yard once, so I know 1st gear works :).  I just hate continuing to dump money into something that would have been better parted out. Any advice for me? Thanks.

Update: I took it out and rode it yesterday. A local mechanic told me that is what he would do to see if some of the smoke cleared up just from sitting too long. Well, it didn't. It was shooting black oil out the tailpipe enough to get my taillight and tire pretty splattered. I could here what I assume to be the piston rattling when I got up the RPMs a little. I definitely think I want to do the top end myself after the local shop told me it would be about $700 for them to do it. Any thing I should be aware of before I delve into it? Do I need any special tools? Thank you.

Danny

Edited by Squibbert

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i did this a year or so ago, all pretty straight forward. i bought a wiseco piston kit off ebay and have been very happy with it.

the valves if you need them can be got from a boat chandlers as they are the same as an outboard - same part no - google it or let me know and i can dig out the details. about half price IIRC

 

 

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Thanks FFMan,

Would you recommend I take the head and cylinder off and take them to a shop so they can tell me what all needs to be done, then I can order the parts and do it myself? I could go ahead and get the piston kit ordered, but I don't know if I would need to order the standard 85mm or the 86mm kit until I see the condition of the cylinder. 

 

 

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Recently got one of these same year and everything. Beat you though as I got it for free ;)

 

Just wanted to say that before tearing anything down  (even though it sounds like you know what you are doing if you rebuilt an xt350 double carb with no schematic ) that you should go ahead and purchase the Clymer manual. Incredibly thorough and detailed about all aspects of the bike. Still available from alot of places. I got it from Barnes and Nobles.

 

 

 

Good luck though it is really a fun bike. Taking a point from the infamous xt350 review video here but I find that riding this bike on long twisty roads provides some great time for some deep thought... about life in general, how much you love the bike... but also a bit of "why does this thing Im riding have two carbs and dual overhead cams?"

Edited by Thatslyb

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if your machine shop is close, take the stuff down there and get some advice. i did that and my man said just hone it and put rings in it. if you need a bore, get the piston kit first and take it to the machine shop so they can get it right.

same with the head, see what they think of the valves, i replaced them on mt xt350, but on my xr250 i just lapped them in as they were good. it does take a trained eye to spot good from bad

 

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Thanks for the advice. I tore into it after work yesterday. Just as I was pulling the cylinder up from the case I heard something drop down inside - OH CRAP! I don't even know what is was. I thought I was being really careful. I didn't have nuts or bolts sitting on top of the case that could have fallen in. It must have been something that was stuck to the bottom of the cylinder. I know I am not going as far as slitting the case open. It might be time to part it out, but what a pain! I better stick to my day job!

And, yes...I was wondering when I got this thing why it had two carburetors and two exhaust ports. I thought it was a twin when I bought it. 

Edited by Squibbert

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might have been a dowel - you might be able to shake it out.

 

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I was wondering about about a dowel. I guess I need to take inventory of how many I can account for and how many there are supposed to be. Not looking forward to taking the motor out of the frame, but I guess that is probably my best option. Thanks FFMan!

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On 5/11/2017 at 11:52 PM, Thatslyb said:

Recently got one of these same year and everything. Beat you though as I got it for free ;)

 

Just wanted to say that before tearing anything down  (even though it sounds like you know what you are doing if you rebuilt an xt350 double carb with no schematic ) that you should go ahead and purchase the Clymer manual. Incredibly thorough and detailed about all aspects of the bike. Still available from alot of places. I got it from Barnes and Nobles.

 

 

 

Good luck though it is really a fun bike. Taking a point from the infamous xt350 review video here but I find that riding this bike on long twisty roads provides some great time for some deep thought... about life in general, how much you love the bike... but also a bit of "why does this thing Im riding have two carbs and dual overhead cams?"

That my friend is the $64,000 question.

The answer is IMHO so you could have your cake and eat it too.    Yamaha did the double overhead cam and four valve thing because to make the engine breathe like a wind tunnel at top end. 

This is all good for top end but sacrifices low end. Enter YDIS.

Pretty fraking clever it is. First you get tumble for good air fuel mix then ya get cylinder swirl to stuff a little bit extra of that fuel air charge in there. But wait there's more.

The dual carbs..that's how we get good intake velocity at low and at high end.  The primary venturi does a good job mixing the fuel and air and "passing gas" up to the point where the engine need more air flow than can pass through the venturi. Then the secondary starts to open up providing the additional volume.

 

YDIS01.png

687687.jpg&sp=3568a76b0accca5e4286e935dd

 

The end result of all this was these XT's had more of what you needed out of the engine both on and off road that earlier designs.  The quench chamber head also gave better combustion efficiency for better power and improved fuel economy along with better emissions.

 

Edited by Eatmore Mudd

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