Fired up '89 XR600 after rebuild. Couple questions.

I finally finished rebuilding the engine on my '89 XR600 and fired it up for the first time tonight. First thing I did was check to see if oil was getting to the head by cracking open the upper oil pipe bolt, and yes oil immediately started pumping out.

I then took it for about a 20 min. ride to break it in. During this ride I noticed a few things. (Sorry for the long e-mail below. I tried to explain everything while it is still fresh on my mind!)

First thing was that the engine makes sort of a clanking noise when it is running. Almost sounds like a rod noise. I have never paid attention to how other XR600's sound, so I am not sure if it is normal. It is not really bad, but noticeable. It did the same knocking noise before I rebuilt it. I double and triple checked all my clearances, but maybe the lower part of the rod is out of spec. It did have a tiny bit of play in it, but I didn't pull the cases apart so I couldn't measure it. The bike runs pretty good, and when it warmed up, it seems to quite down a bit. I"ll be taking it to a local motorcycle shop to have them listen to it. The guy has tons of XR experience so he should be able to help me out.

The 2nd thing is that the bike STILL smokes a little. Nothing compared to how badly it was before, bit it is still smoking. The only way I could tell was when I was stopped at a stop light, and I could see smoke across my headlight. When I got home I noticed the rear fender had started accumulating a bit of oil on it after only 7 miles of riding. Before the rebuild, after 2 miles of riding, the rear fender was dripping with oil, so it is not nearly as bad. I am a bit lost now. Maybe I should have changed the cylinder since it was right at the service limit. But I replaced the rings, and oil seals and had a new valve job. The oil must be blowing by the rings right at the top of the compression stroke. I'll have to see what I can do about this.

And lastly, the bike has always idled a little funny. It seems to miss a little at idle. Also, the idle is erratic. Sometimes when I rev it up, it will stay at a high idle, and other times when I give it a quick blip of the throttle it will drop down to a nice low idle, but then it sometimes creeps back up to a high idle. Most of the time though, when I am down shifting and coming to a stop the idle stays high, and I have to blip the throttle to bring it down. I went through the entire carb and cleaned everything out. But I didn't replace anything since it all looked pretty decent. Should I spend some money on one of those carb rebuild kits? Any other ideas.

Thanks for any help. I have spent so much time rebuilding this bike from the ground up and making it in like new condition, so I hope to take care of these last few issues even if it means pulling the motor apart again, or splitting the cases. I'll do whatever it takes.

well you said you just rebuilt the engine correct then i would expect it to smoke from all the oil you rubbed over everything when putting it back togethor, also i think it would be better to invest in an aftermarket carb,and i could be wrong but i thought all xr's made somewhat of a engine noise, but good luck im putting my 89 xr600 back togethor as well and im just waiting for the kibblewhite valve srpings to come in the im all set, but i hope to hear you get it all worked out

Let us know what you did. I'm thinking you did a top end rebuild. New piston, etc. Did you get the head worked on? New valve seals?

From reading here, it seems like the proper ring break in method is to ride it pretty hard. Not endless 90+ mph runs, but some good short wide open runs. I did a 200 foot hillclimb, over, and over again.

My XR600 has always made a lot of worrisome noise. So far none of it has been an issue. The plan of taking it to the shop is a good one though. It should put your mind at rest. The spec on the lower end rod clearance is pretty large. You check by just pushing and pulling on the rod, no need to split the cases.

If you want to hear something scary, check out a brand new CRF450. One of my friends got one. It made the most god awful clank clunk racket, I was amazed.

For the unstable idle, check for carb leaks. I spray carb cleaner over the rubber boot that goes between the engine and the engine. The idle goes up when you spray hits the leak. I've had issues with the boot to engine seal before. The o-ring in there gets all flattened out and doesn't seal.

Oil coming out of the exhaust and collecting on the fender is not good, sounds like oil is being pumped past the rings. Give us some more info. Did you mic the cylinder to check for wear, taper and out-of-round? Did you measure the ring end gaps to see if they were in spec? Did you install a new piston? Did you replace the valve stem seals? Did you check the valve guides for wear?

All the big XRs have some Counterbalancer backlash noise especially a low rpms, there's no adjustment and 1 cylinder engines are not smooth at low rpms so it can be noisy but not a issue.

I installed a new camshaft, new rocker arms, new outer valve springs, new seals, new rings, and a new clutch. I also had a valve job done on the head.

I went by the shop today and he listened to it for about 5 seconds and aksed if I had replaced the timing chain. I said no, and he said that was the clanking noise. Who knows how old it is, and I should have replaced it.

I did mic everything on the engine that I had access to. All the head components were perfect. The guides, valves, piston and pin were all well within the service limits. The upper rod bore was around .001" out of the service limit. But It did not concern me since the rod to piston pin clearence was still well within the service limit.

The oil problem (which I was afraid of) is most likely the cylinder. I purchased a dial bore indicator before I put the cylinder back together and at the bottom of the cylinder it was .002" out of round with the larger diameter still within the service limit. The middle of the cylinder was .003" out of round, but still the larger diameter was within the service limit. Now at the top of the cylinder, it was .004" out of round (where .003" is the max), and the larger diameter was .002" past the service limit. Since the cylinder is nikasil, I couldn't bore it, so I figured I'd just run it. Well, that's most likely why it is still smoking a bit. The oil is pushing past the rings at the top of the stroke. I'll just keep an eye on the oil, and if burns to much, then a new sleeve and piston/rings will be next. Maybe I'll just do it when I change my timing chain. But if I go that route, it might make sense to also change the rod since it is a little out of spec.

As far as the idling. I did spray carb cleaner around the intake boot on the engine and carb, and on the throttle shaft, and choke shaft, but the idle never increased. It does sound just like an air leak, but I couldn't find it. I'll just pull the carb apart one more time. The first time I pulled it apart, I just cleaned it and re-used all the seals since I was going to the desert the next day and their was some dirt in it that wouldn't let me go full throttle! So I may just need to replace some old parts in it. Hmm. I actually have another carb off of my 1993 parts bike. Maybe I'll try that if the jets are all the same.

Thanks for all the ideas. Lessons learned, follow the service limits in the manual when it comes to the cylinder tolerences, and change that timing chain!

This may sound stupid, but did you lube the piston when you installed it? I use to always lube it when I installed a new one just like the service manual says, and I always had them burn oil. In the 450 forum there has been several discussions on dry installations so I thought I would try it, and I've had 2 successful non-smoking rebuilds since then. From now on it will alway be dry installs for me. My xr is an 1988 and is basically identical to yours and I rebuilt my carb with one of those $10 kits off of ebay and have been very happy with it. At $10 it might be worth a try.

I went by the shop today and he listened to it for about 5 seconds and aksed if I had replaced the timing chain. I said no, and he said that was the clanking noise. Who knows how old it is, and I should have replaced it.

I did the same thing when I had my head rebuilt a couple of years ago. I had it apart again a month later to do the chain. Replace the tensioner too, both the inside piece (the bolt) and the ratchet part. When I got the new chain, I compared it to the old one. They sure looked the same length to me. So I figured it was the tensioner that was bad. Bike ran better and much quieter afterwards.

Thanks for the tip on the tensioner. I wouldn't have even thought of replacing it. I guess it would make sense to buy a new spring to complete the assembly. How to you check those? Mine seems to be working properly. The one way bearing doesn't slip. Is the tensioner spring the only thing keeping the tension on the chain? If so, maybe just a new spring would be good enough.

Did you replace the guides? Mine look ok, but I don't know what a new one looks like. I think I might also replace the cam sprocket. It had some tiny wear marks on the teeth, but for $20 buck or so it might be worth it.

So I'm looking at a complete new tensioner (maybe just a spring), cam chain, cam sprocket and valve cover gasket. I should be able to re-use my clutch cover gasket since it is new.

If the chain/tensioner is that bad to slap around, maybe thats why it is missing a little at idle. Hopefully a new setup will take care of it.

Thanks again.

I only replaced the tensioner bolt, the ratcheting part, and the chain. Guides didn't look too worn. Yes, that is the only spring holding tension on the chain. For the gaskets, you should be able to reuse. You can reuse even if the gasket splits, just put a thin film of silicone on there. I've reused the side cover gasket several times that way. With my last rebuild, I'm using aftermarket gaskets that don't have the glue on them. They are a lot easier to reuse. I just use the silicone on them.

I think the hardest part of rebuilding is getting those darn gaskets off. I spent several hours with a propane torch and a scraper.

I agree, those gaskets were a pain. I used an air grinder with fine wire wheel. Worked pretty good. I used a scraper on the harder stuff.

That's one of the main reason I don't mind pulling it apart. There will be no gasket clean up. I should easily be able to pull it apart, put the chian and tensioner in it and back together in one evening.

Could you point out what you replaced on this diagram? cam chain

I think you are talking about #6 and #9.

How could you tell they needed to be replaced. Not sure what to look for. What did the old one feel like compared to the new one? I just don't want to spend $60 on a new tensioner without knowing for sure if I need a new one.


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