Jump to content
Sign in to follow this  

'86 250 rebuild followup

Recommended Posts

All last summer & fall I rebuilt an '86 XR250 engine, which is installed in an '84 XL. I used the Wiseco 77mm kit along with a Hotrods conrod. And with a few new bearings, new valves & springs, valvestem seals, all the oil seals, all engine gaskets and even replaced a bunch of case bolts. Some Helicoils had to be installed on various 8mm bolts. Some of you asked to hear more about it when it's running, so a little after the rebuild impressions here at over 1000 miles.

Keeping in mind I still haven't gotten a proper air filter installed, so I haven't done any tuning to the carb. But, the bike is noticeably better in power. Still hard to start first thing in the morning though. I'm thinking about adjusting the compression release all the way back. It's almost all the way now. Maybe even just not use it?

I think I'm hearing the valves rattling, and there's a popping sound that wasn't there before. Sounds like an empty soda can on the exhaust, but it's coming from the head. The rattle & pop are two different sounds underlying the exhaust. That's three engine sounds total. Not worried about the third one. I'm wondering if I need to go higher on octane? I switched to mid-grade, but I'm thinking about dumping that into my car and refilling on the highest pump gas.

I decided to check the valve clearances a 6th time, going for a really tight pull on the feeler gauge. Then an extra quarter turn tighter. Seems to have quietened down the more tickier rattling but not the pop-can popping. That rattle would go away while idling, if I raised the rpm's slightly. Which is why I decided I wasn't getting the valves tight enough.

The pop-can sound has me wondering if that's knock I'm hearing. Seems to just be there at all speeds & loads.

Besides all that, riding on dirt roads is fun now. 3rd & 4th, snap the throttle open and the rear kicks out a bit, rpm's run up a little until the bike gets going faster and then the engine settles down and the tire starts grabbing. I think I'm going to need a new rear tire soon, if I keep that up!

I'm not sure what the top speed is as I'm not sure how many rpm's I'm running, but before the rebuild I could barely get over 60MPH, now I'm at 70. But I like how it sounds at 55, going as slow as 40 in 6th without needing to downshift to accelerate again on a flat road. A very nice ride overall.

The JB Weld seems to be doing well inside the engine case. Nothing weird happened yet!

And while I had the elbow room, I got in there and really turned the rear spring nuts all the way up the shock. Then had to go back some because the spring was free-floating. But I fixed the steering issue by lowering the rear-end. No more tuck-in when I relax and forget to keep the steering steady. No more tank slap while adjusting a mirror! Plus I can get both feet on the ground.

I didn't think it was worth taking plain pics. If you've seen an '84 XL then you've seen this one as it looks the same now as a 280, as it did when it was just a 250. I'm looking at getting some video soon, it's just not sounding as good on camera as it does by ear. I need a better camera...

Total bill for the rebuild was about $1350, all because I forgot to check the oil.

Share this post

Link to post
Share on other sites

Well, might as well add onto this instead of starting a fresh thread.

I finally just had to take the rocker cover off to see what's going on inside the top of the engine. Bad news is what. All four cam followers are shot and the cam lobes have all kinds of flat spots, including a noticable loss of the top of the lobes.

I think I finally figured out why I could never get the valves to run quiet. The cam must have been bad all along, it was just too subtle to tell last time I looked at it. It's not so subtle now...

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