XR250R On Going Top End Issue - Need Help

[andy_t]

Sorry this is a bit lengthy....

I have an '01 XR250R that I originally burned the valve guides/seals on using the decompression as a compression brake riding some hills last summer. The result was burning oil. The exhaust valve lash seemed sloppy so I tightened them up. That worsened the problem. I took the bike in to a local shop that has a good reputation. The net result was to replace the piston & rings and do a complete valve job. The shop had the bike for a month... the owner told me they had problems with something to do w/ the decompression mechanism when reassembling the engine. He ended up buying a Honda factory shop manual to figure out the issue. [This is still unclear to me since the decompression is nothing more then a cam that rotates to engage the rocker to open the right side exhaust valve]. I was careful to break in the engine before riding it hard. At first it burned a little oil, no big deal. However the more I rode the worse the oil burning became. After about 50 miles the bike was puking out more blue smoke then a two-stroke! I figured the rings didn't seat properly. Compression was +/- 90lbs. I did a pressurized leak down and found a 30% loss through the bottom end; bad rings! This time I tore it down. I took the cylinder to the area machine shop that is used by the factory shops and everyone else in the area. I figured that I'd start over from the beginning since I didn't do the original work. I had the cylinder bored to .020” over and put in another new piston and rings. Making sure that the stamping on the rings were facing up, and that the oil scraper rings (top and bottom) were install 180 degrees opposite in line w/ the wrist pin, and the 'waffle' ring ends were butted; not overlapped [common problem]. I ran the bike for about 5 miles up and down my street for break in with little blue smoke. Took the bike to the trails and ran it for a total of 10 miles with mild oil burning. After each ride I cooled the engine and checked the value clearance. Took the bike back out [different day] and ran a few hot laps of 5 miles each, letting it cool completely between rides. By the end of the third ride the engine was burning oil like a two-smoke again! I have less then 50 miles on the piston/rings. The only thing that is common about this problem is the piston/ring manufacture; Wisco. I did another leak-down and I'm once again blowing air out the bottom end. Anyone else have any ideas, or recommendations on other piston manufacturers?

[Red_Snapper]

At only 50 miles didn't you feel like communicating with the shop that did the work before tearing it down and rebuilding?

What kind of oil are you running for break-in?

Are you following the correct method for checking the oil level? Alot of people badly overfill this bike thinking it has a conventional wet sump.

I doubt you will find a problem with Wiseco pistons, they are in XRs everywhere and running fine, mine included.

[thedude05]

First off, Wiseco is not the problem. I just put a wiseco std bore piston in my 2002 250 and I have no issues. If it made you feel better you could buy a OEM Honda piston and ring set, although I think you are going to have the same outcome.

Second, You broke it in wrong, sorry but you did. I don't mean to sound like a smart ass or anything I'm just relaying the information that I found out when I put my piston in. With modern 4-strokes you must break them in HARD!!! I rode my bike harder on break in than I have ever ridden it. The key is hard acceleration and deceleration, not just holding it wide open either, you have to vary the RPMs and really get the piston moving around in order to seat the rings.

Third, did you supply the machinist boring out you cylinder with the new piston and recommended clearances?

Fourth, What was your piston-to-cylinder wall clearance?

What I would like to know, it's not really related to the piston issue, is what confused the shop about the decompression system?? ?

It sounds like you did everything right on assembly. When you removed the old piston, did you notice any damaged rings or anything out of the ordinary?

Let us know, I'd really like to help you figure this out.

[andy_t]

First, thanks for the replies... as I'm really stumped!

As for oil use: After the first replacement I used Honda 10/40 non-molly synthetic. The old guy that did the boring recommended 20/50 conventional (20/50 since it's been so dang hot around here).

Break-in: First piston was moderate revs leading into harder revs on the trails. The second piston I started out easy because I put in a HotCams ? cam and they called for no hard revving. In both cases the revs were varied. Furthermore, by the time I got to the trails I didn't hold back. Each time the bike had 5 to 10 miles on it.

The machinist that did the bore supplied the Wisco both time. He was also the one that did the valve job. I talked to him extensively before he/we did the second piston. He's been around bikes for fifty years, and he does all the head and cylinder work for all the shops (factory and independent) in the area. Mori "is the man" when it comes to this...

Oil Level: (Red_Snapper) SPOT on comment about checking the oil level. I made that mistake the first time I changed the oil. Oil level is correct.

Piston: I can't believe it's a Wisco problem either since I've used Wisco on other machines. However..... two times, same issue, both related to the rings. It makes me wonder.....

One thing I *did not* check at Assembly was the ring gap. That being said, I had no reason too since the bore was +.020 and the piston was matching.

So I'm faced with doing it again, I'm just checking twice before I begin, and I'm going to try a different piston mfg.

andy t.

[Red_Snapper]

First, thanks for the replies... as I'm really stumped!

As for oil use: After the first replacement I used Honda 10/40 non-molly synthetic. The old guy that did the boring recommended 20/50 conventional (20/50 since it's been so dang hot around here).

You should stay away from synthetic on a top end break-in for a few hundred miles, at least.

[andy_t]

Yup... using regular oil now. But this isn't the cause of the oil burn issue.

I'm thinking of pulling it apart and checking the ring gap; it doesn't take that long anymore since I've done it a few times now. I might even by the 75.5mm ~ 78mm ring set and file them myself to ensure I get the OEM gap. Thoughts?

andy t.

[thedude05]

Umm... You should not use synthetic oil on break in ? That probably caused your rings to not set. Also you should have set your ring end gaps before putting the piston in, if they aren't right, that could also be causing your oil usage.

Don't use the OEM gaps, they won't work with the Wiseco piston. The first ring should be set between .011 and .012, I don't remember the second ring, you'll have to call them, and the oil control rings can be put in without setting gaps.

You probably will have to buy a new set of rings. This time, DON'T USE SYNTHETIC!!! And set your end gaps per wiseco specs.

[Red_Snapper]

I would follow the piston manufacturers instructions, explicitly, for bore dimension and end gap on your specific size piston.

Here's some interesting reading about break-in if you haven't seen it already.

http://www.mototuneusa.com/break_in_secrets.htm

[creeky]

I have installed quite a number of Wiseco pistons in XRs and have never had a problem. Your situation sounds like the rings are not seating. First of all, the cylinder must be honed properly. The piston-to-cylinder wall clearance must be correct. The ring gaps have to be checked for proper end gap. The ring gaps should be staggered according to the manufacturer's instructions. You have to use non-synthetic oil for break-in, using synthetic prevents the necessary ring-to-wall friction necessary for seating. Your problem lies in one or more of these areas. The rings should seat in the first 15-20 minutes of running, don't baby it, go a little easy for a few minutes, then accelerate and decelerate each time revving it up a little more on acceleration. Do this for 15-20 minutes, the rings should be seated.

[andy_t]

Ok... I guess this is what I'll do then. 1). Order another set of rings and top end gaskets. Cost = $50.00. 2). Tear down the top end. Cost = 1.0Hr. 3). Install new ring set and put it back to together. Cost = 1.0Hr. 4). Change oil, using conventional petroleum oil. Cost = $6.00. 5). Take it to the woods and ride it as hard as I can. Cost = Priceless ?

andy t.

[4strokeridertt]

Double check the valve stems and guides for wear. I just pulled mine apart and tossed in new seals and it still smoked on startup (sure sign of worn seals). Pulled it apart again and measured the stems, exhaust are worn quite a bit so I ordered new ones. I should have it back together on a few days.

[redrider7202]

Ok... I guess this is what I'll do then. 1). Order another set of rings and top end gaskets. Cost = $50.00. 2). Tear down the top end. Cost = 1.0Hr. 3). Install new ring set and put it back to together. Cost = 1.0Hr. 4). Change oil, using conventional petroleum oil. Cost = $6.00. 5). Take it to the woods and ride it as hard as I can. Cost = Priceless ?

andy t.

Don't forget to get it re-honed... otherwise ur gonna be back at square one... again

[Red_Snapper]

Sounds good, but you shouldn't ride it "as hard as your can" during break-in. Ride in a spirited manner. Roll on--roll off. Stay reasonable, but on the aggressive side.

BTW, when you get your cylinder back from machining, you need to clean it scrupulously. Soap and water followed by oil wiping until there is no more honing residue.

[TMX]

I'm having a hard time getting past that 30% leakdown rate, seems awful high just for new rings that haven't seated.

Was there any damage to the first new set of rings after you pulled it apart again or any scoring on the cylinder wall?

-B

[andy_t]

replies to all....

When I take it apart I will rehone it on the drill press. Cleaning is a "yes" with hot soapy water, the wipe w/ clean lint free cotton until there is no gray residue. As for oiling the cylinder before installation. I was instructed *not* to use oil w/ the Wisco. Rather spray w/ WD-40 to coat the wall then install the piston. I believe the value stems and seals are all OK. The head has less then 75 miles on it since a complete valve job. Also, there is no leakage detected by a pressurized leak-down.

[TMX] I'm using a Snap-On leak-down tester and it's showing almost 30%. Also, you can hear the air blowing into the crankcase. I forget the actual compression number, but it's less then 100 now. I tested it before I fired up the engine [after new piston & rings and new HotCams], and I believe the number was around 126 ~ 130 dry. And, "no", I haven't done a wet compression test to see if it goes up. With air blowing out the bottom I figure what's the point.

I do have one other question for those of you that have installed Wisco's. Did you measure the ring gap? And have you ever found any rings to be out of tolerance; too large of gap?

andy t.

[Red_Snapper]

replies to all....

Cleaning is a "yes" with hot soapy water, the wipe w/ clean lint free cotton until there is no gray residue. As for oiling the cylinder before installation. I was instructed *not* to use oil w/ the Wisco. Rather spray w/ WD-40 to coat the wall then install the piston. andy t.

It is recommended to wipe the cylinder using oil to further clean any remaining honing residue.

Never heard of not oiling the cylinder prior to installation. It's hopefully going to get oiled shortly after the engine is started--the question is how long will it take? Any oil you add will be cheap insurance and will be quickly wiped by the oil wipers. WD-40 in the cylinder? No way, but suit yourself.

My Wiseco ring gaps were spot on, but then, so was the bore job.

[creeky]

replies to all....

When I take it apart I will rehone it on the drill press.

[TMX]

I do have one other question for those of you that have installed Wisco's. Did you measure the ring gap? And have you ever found any rings to be out of tolerance; too large of gap?

andy t.

How do you get a good cross-hatch pattern on the cylinder wall with a drill press? Maybe I can learn something new here? I have never found a Wiseco ring to be out of spec on the end gap. If the end gap is out of spec, suspect the cylinder bore to be incorrect and measure it.

[ande0652]

I am very interested in this thread. I too have the identical problem. I have had two different pistons/sets of rings. I am convinced that is not the problem.

I have spoken to many people about this problem. One very reputable guy told me that this problem is cause by the lubrication system. If there is a problem with the oil not being pumped up into the frame, it causes too much pressure build up in the crankcase. In turn, the oil will be blown by the piston from the BOTTOM. There is a check valve in your oil pump. This could be the problem. I tore mine apart and did find a problem with the check valve. I rebuilt it and it did quit smoking for a brief time. I have now ordered a complete new oil pump.

[andy_t]

The oil pump is news to me.... That's good information.

Here's the latest:

In the process of tearing down the top-end I noticed a *lot* of oil in the left exhaust port and head pipe. The right side was dry and carboned as one would expect. I took the head back to the machine shop that's done all the work. One thing we noticed was oil leaking down the valve stem. His thought was perhaps the wrong size seal was installed since they all look alike. {His bench has several bins of seals of different sizes. They all look a like and a larger one could have gotten mixed up with the correct ones.} So he removed and replaced the seal.

I put it back together and ran it up and down the street. Once I got all the oil out of the pipe it wasn't smoking much. Took it for a hard ride last weekend. Smoke, Smoke, and more Smoke!!! ARGH! Tore it back down on monday and took the head back into the shop. Same symptoms.... oil in the port and on the stem. However, a wet leakdown shows no sign of trouble. Since the stem was just out of tolerance I asked him to replace it. In addition I've asked him to install a new valve guide and seal. So, a complete rebuild of that valve. I'm waiting to get it back.....

The only other thing we think it might be {at this point} is a small crack somewhere in the port. I put contrasting dye in the oil before I ran it in hopes I could see something that would lead me to the problem. The port of course glowed yellow because of all the oil. However, there was one spot that looked different under the black-light. Almost like a rust spot {I'm thinking a heat spot} compared to the rest of the port.

Once I get the head back and put it together I'll update this post again....

andy t.

[Vintage Not Pimpage]

Sounds like it could be a worn out valve guide. Did you measure the radial play of the valve stem in the guide when you pullled it apart?