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Old Today, 06:28 AM   #1
Noahlov3 OP
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Location: Brooklyn
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XT500 engine rebuild

Hey Ya'll.

Purchased my first 4-stroke bike this winter and couldn't be happier. Rode it up from Philly to Brooklyn and then she shit the bed, backfiring, wont start. Anyways, a bike shop and a couple hundred later we realize I need to do a top end rebuild. Does anyone want to help me or know anyone in Brooklyn that is familiar with XT500 rebuilds?

I can tune and build 2-strokes and am familiar with working on engines but this is my first adventure into 4-stroke and would be nice to have someone who knew what they were doing since its a whole new set of things to learn. Free beers.
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Old Today, 08:24 AM   #2
montesa_vr
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You might want to double post this in the appropriate regional forum.
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Old Today, 09:23 AM   #3
Sidecar Jockey
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I got your PM. Post some pictures of the bike!!! I'm curious to see if this is my old one!

Before you take anytihng apart, or let a shop mess with anything (in my experience, most shops don't know anything about these old bikes), do the following:

1) Compression test. It should have ~120+ PSI. If you don't have a compression gauge, kick it over WITHOUT using the compression release. It should be hard to kick on compression stroke. If its hard to kick, you're OK. If it doesn't seem to have compression, check the adjustment of you compression release cable. Sometimes this cable gets too tight and causes the release to hang slightly open (this happened to me before, and it took a whole weekend of head scratching for me to figure it out). This will cause the "backfiring, wont start" symptoms. If it doesn't have compression and the release isn't the issue, then you could have a real problem.

2) Clean the points and check the timing. Your description of "backfiring, wont start" sounds exactly like fouled points or slightly off timing. These bikes are VERY sensitive to both, hence their reputation for being hard to start. The service interval for the points on these old bikes is only ~1,000 miles...

3) Check and re-torque your exhaust flange bolts. These vibrate loose all the time on my XT500's. A loose exhaust flange will cause an exhaust leak, which can make it backfire, have a flat spot/studder when running at a certain RPM, or make it hard to srart.

4) Clean your carb. If your polit jet is clogged, its just going to pop and fart, but wont start. Was it sitting for a while? I dont like to let gas sit in my carbs for more than a month...


What was it like the last time it was running? Did it smoke? Did it make any noises? Did it die on its own, or did you turn it off?

Unless it started smoking alot or something went 'boom', I highly doubt that you need a top end job. These are very robust motors. What did the bike shop say the problem was? Why do they think it needs a top end rebuild?

Post back with info about my #1-4 above, what the shop said, and describe what happened last time it was running. That will let us better advise / diagnose your problem.

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Old Today, 11:14 AM   #4
Chico
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I used to have an sr500 and did the top-end on it. It was really simple if you go slow and have a book. First time I had ever done anything like that.

Also, here is the place to ask questions specific to those bikes:
http://www.sr500forum.com/forum/

Here for parts:
http://www.thumperstuff.com/
Great guy and knows the bikes inside and out. Give him a call rather than email.

Invaluable resources.

And this:
http://www.advrider.com/forums/showthread.php?t=326246&page=49
Like sidecar said, eliminate everything else before pulling the motor out. What is the precise diagnosis?

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Old Today, 11:29 AM   #5
plugeye
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and this site

http://www.xt500.co/index.php?sid=8f...ea00cf49830aca
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Old Today, 12:05 PM   #6
Noahlov3 OP
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Quote:
Originally Posted by Sidecar Jockey View Post
I got your PM. Post some pictures of the bike!!! I'm curious to see if this is my old one!

Before you take anytihng apart, or let a shop mess with anything (in my experience, most shops don't know anything about these old bikes), do the following:

1) Compression test. It should have ~120+ PSI. If you don't have a compression gauge, kick it over WITHOUT using the compression release. It should be hard to kick on compression stroke. If its hard to kick, you're OK. If it doesn't seem to have compression, check the adjustment of you compression release cable. Sometimes this cable gets too tight and causes the release to hang slightly open (this happened to me before, and it took a whole weekend of head scratching for me to figure it out). This will cause the "backfiring, wont start" symptoms. If it doesn't have compression and the release isn't the issue, then you could have a real problem.

2) Clean the points and check the timing. Your description of "backfiring, wont start" sounds exactly like fouled points or slightly off timing. These bikes are VERY sensitive to both, hence their reputation for being hard to start. The service interval for the points on these old bikes is only ~1,000 miles...

3) Check and re-torque your exhaust flange bolts. These vibrate loose all the time on my XT500's. A loose exhaust flange will cause an exhaust leak, which can make it backfire, have a flat spot/studder when running at a certain RPM, or make it hard to srart.

4) Clean your carb. If your polit jet is clogged, its just going to pop and fart, but wont start. Was it sitting for a while? I dont like to let gas sit in my carbs for more than a month...


What was it like the last time it was running? Did it smoke? Did it make any noises? Did it die on its own, or did you turn it off?

Unless it started smoking alot or something went 'boom', I highly doubt that you need a top end job. These are very robust motors. What did the bike shop say the problem was? Why do they think it needs a top end rebuild?

Post back with info about my #1-4 above, what the shop said, and describe what happened last time it was running. That will let us better advise / diagnose your problem.

Thanks for the awesome reply...good to hear someone had a passion for these rad bikes.

Ok here we go...

I parked it in Philly after I bought it for the winter and didnt touch it for 3 months. Got to Philly and she started up just fine. Rode her around, no sweat. Next day rode her to NY and everything was a blast. She sat for a week in the garage and I went to bring her out again and wouldn't start and backfired once or twice. My thought was carb was gunked up (problem No.4) cleaned it up and still got a backfire or two and no start. 1st gear was suck for some reason too so I decided to bring it to a shop.

Drug it to a moto shop had them look at it. They adjusted some cables and the clutch went free, did another carb clean and the bike started. Needs an exhaust gasket and a diaphram gasket, no prob. Went to pick it up, started once idled, paid the guy, went to go kick it and wasnt starting. Kicked it over once and it started but then the engine oil spat out the overflow and I killed it to see what was up. After that it just kept backfiring and not starting and thus finally ramming my knee into the tank for me to take a breather.

So I'll go and ask them about #2 and #3. #1 and #4 are checked off though. I'll grab some pics this afternoon. THANKS!

Noah
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Old Today, 12:37 PM   #7
Sidecar Jockey
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Quote:
Originally Posted by Noahlov3 View Post
My thought was carb was gunked up (problem No.4) cleaned it up and still got a backfire or two and no start. 1st gear was suck for some reason too so I decided to bring it to a shop.

Drug it to a moto shop had them look at it. They adjusted some cables and the clutch went free, did another carb clean and the bike started. Needs an exhaust gasket and a diaphram gasket, no prob. So I'll go and ask them about #2 and #3. #1 and #4 are checked off though. I'll grab some pics this afternoon. THANKS!

Noah


The clutches on all 3 of mt XT500's stick if they sit for a week or so. Its normal. Work it in and out a few times and the come free. I dont know why, but it always happens.

The exhaust gasket and carb diaphragm were replaced? Or do they need replacing?

You didnt specifically mention compression (#1). Does it have compression? Was it smoking when it ran? If it has compression and wasnt smoking, I'm 90% sure your top end is fine.

Puking oil is probably from over filling and wet sumping. The oil tank is in the frame, so no oil should be in te crank case. If the check ball sticks (which is also pretty common) it will wet sump. Excessive wet sumping will make it barf oil. A bike can wet sump the whole oil tank down in one night.


Get as much info as possible and post it here before paying someone to work on it. I bet we (forum members) know more about these bikes than the guy at the shop...

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Old Today, 01:49 PM   #8
Noahlov3 OP
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Quote:
Originally Posted by Sidecar Jockey View Post
The clutches on all 3 of mt XT500's stick if they sit for a week or so. Its normal. Work it in and out a few times and the come free. I dont know why, but it always happens.

The exhaust gasket and carb diaphragm were replaced? Or do they need replacing?

You didnt specifically mention compression (#1). Does it have compression? Was it smoking when it ran? If it has compression and wasnt smoking, I'm 90% sure your top end is fine.

Puking oil is probably from over filling and wet sumping. The oil tank is in the frame, so no oil should be in te crank case. If the check ball sticks (which is also pretty common) it will wet sump. Excessive wet sumping will make it barf oil. A bike can wet sump the whole oil tank down in one night.


Get as much info as possible and post it here before paying someone to work on it. I bet we (forum members) know more about these bikes than the guy at the shop...
Yeah it has tons of compression. It was constantly smoking, not a lot, but smoking. When I fired it up there was a big plume but it burned away after it warmed up. I haven't installed the diaphram and the exhaust gasket yet.
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