New rings or new 100mm piston ???

Greeting group.

First post from a long time rider and wrench. I am the happy owner of a 2006 XR650L. Very nice bike with 12,000 miles on the clock. It starts and runs well BUT the infamous oil smoke is present. Actually I was smoking a lot after trying to ride some wheelies. I did see a faint puff of smoke at the top of the head. Gasket possible? Since I had little idea how the bike was treated I decided to pull the top end. Little to no wear on cam and rockers.

Valve guides and seats like new / no play. Valves seal 100% so I cleaned the head and ports and new Viton stem seals installed.

I just measured my cylinder and piston. No taper or issues with the cylinder. Piston is at the service limit for diameter so I am planning on breaking the glaze on the cylinder and put new ring on.

I am torn between getting a new JE forged piston or just Honda rings.

If you were buying rings where to shop and what would you do ???

I have always had a motorcycle since I was a kid (48 now). I raced motocross years back and always wanted an on / off road bike. The 650L I have just popped up and I could not resist. I can tell from the part (exhaust and K&N filter someone has wrenched on it. The smoke problem I have no clear idea where it was coming from but by doing the top end hopefully I nail it and can enjoy riding.

Someone really buggered my intake bolts.

Those look like fun to replace since the heads are almost gone......

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Edited by cal50
better topic refrence

If you haven't thrown the old rings away yet, I would suggest checking the end gap. If it's really wide, then that is likely where the oil was coming from. another common culprit is spent valve seals. Since you're already in there, might as well replace those too.

It's encouraging to see that you have proper inspection tools for this job. Since I see a snap gauge behind the mics, how did the bore spec out? Try honing it and then check again. If the piston clearance is still within limits after that, you could probably get away with just rings and a hone. OEM rings can be had just anywhere that sells OEM Honda parts. The Thumpertalk parts store, Cheapcycleparts.com, BikeBandit, Service Honda, local dealers, etc.

Depending on their condition, the (metal) head gasket and (metal) rocker cover gasket can often be reused. Don't ever use the cheap fiber versions.

Your bike looks to have been reasonably well cared-for, BTW. I would chuck that K&N air filter in favor of oiled foam if the bike will see much dirt, though.

Stock piston: 3.9362 (inch)

Cylinder bore: 3.9395 ( top,middle, bottom. No taper and round).

No scratches or weirdness in the cylinder.

That give me a clearance of .0033 which is on the high side in my service manual for a stock piston. This puts me in the clearance range for a forged piston.

I will check the end gap later tonight.

So would you re-ring with stock rings or go forged / new slug?

(Toolmaker by trade so precision is a good thing)!

What it looked like when I got it-

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So would you re-ring with stock rings or go forged / new slug?

That depends on what you want out of the bike and whether or not cost is a consideration.

That bike looks brand-new. :thumbsup: I see it also has an aftermarket pipe and because of that, I recommend pulling the float bowl to see what jets it has. People neglect the jetting or get it wrong so often that I feel like a broken record when I say that. The color of the plug and exhaust valves usually gives a decent indication, but you already cleaned them. :confused:

That depends on what you want out of the bike and whether or not cost is a consideration.

Cost is a lesser concern. Looking for good power and longevity.

From wrenching on other motors I like the cast hypereutectic alloy pistons for light weight and tight clearance fit. I put forged Wiseco pistons in my Harley and the clearance needed for forged pistons giver it a unique "knock" that forged slugs make.

Where I am at I don't think a re-bore is really justified and I should likely just hone / glaze break it and re-ring.

Is there a trick way to check the valve guide seals?

(Not the valve stem seals).

1.) Cost is a lesser concern. Looking for good power and longevity.

2.) From wrenching on other motors I like the cast hypereutectic alloy pistons for light weight and tight clearance fit. I put forged Wiseco pistons in my Harley and the clearance needed for forged pistons giver it a unique "knock" that forged slugs make.

3.) Is there a trick way to check the valve guide seals?

(Not the valve stem seals).

1.) Then a forged piston seems like the logical choice to me.

2.) I haven't heard too many mentions of audible piston slap when running RFVCs with forged slugs. My 600 doesn't make any noise that I notice. Then again, I have a Ford 5.0 with forged pistons that slap, I had a similar one in the past that did not, and my SVO's 2.3T doesn't have noisy slugs. :thumbsup:

3.) Not with the engine in pieces. One way I have heard of is to ride around for a while, pull the header off after the bike sits overnight, and look for oil on the exhaust valves.

I never did hear the ring end gap specs, I suspect that was your smoke issue. I second the K&N chucking, they let a ton of dirt through. That might be the cause of smoke too.

I have had a Wisco piston in my bike for over 9,000 miles. The headgasket blew due to a pulled stud so I inspected the piston and ring end gap after that mileage and all looked well. Reused the rings since the end gap was nearly what I had set it at originally. Dry reassembly, no hone and running again now with great power and no oil consumption.

I would pop in a forged piston while there, us Honda factory valve seals for best results.

Ok, I just measured the ring end gaps:

Actual .019 (spec .008~.016)

Actual .028 (spec .014~.022)

I did not do the oil ring.

Since these are out of spec I hope this would explain the oil smoke. I don't see a smoking gun anywhere else (pun intended).

If I go Wiseco standard 100 mm what is the ball park comp. ratio? Best place to buy???

Carb removal is on the "to do" list. In regards to the K&N filter I have run them on many vehicles. As long as it's cleaned and oiled I like them. If it's not oiled you can toss your motor.

Someone really chewed up the heads on my intake bolts. Since I have no leaks would you fight them loos and replace or move on to something that needs "fixed"!

There is your smoke. Bet the oil ring is out of spec too.

I run an advertised 11.5 to 1 Wiseco, that measured out to an actual 10.2. Runs good, no excessive ping at 750 ft elevation. Premium pump gas, ethanol free preferred for me.

I still don't like K&N, seen too many dusty intakes with them, and yes they were oiled. Get a factory foam one and be happy.

There will be no easier time than now to attend to the tortured bolts, everything is accessible now off the bike.

There will be no easier time than now to attend to the tortured bolts, everything is accessible now off the bike.

Yep.

I already knew the answer....

Well after considerable reading I think the 600R piston is about ideal compression wise so I have to get one on order soon. From the advise of others I also ordered a UNI filter and will swap out the K&N. Not wanting to re-invent the wheel and with a new bore and piston I really do not want dirt mixed in my handiwork.

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