Engine rebuild options...

[freak_leg]

Ok guys it seems my winter project will be rebuilding Eleanor's engine. Number 1 has a lot of blow by and keeps oil fouling the plug. When the plug does fire it pops pisses and moans and smokes like an old diesel. So ya, the rings are toast. So here is my thinking... Machine costs for the jugs + new rings + probably replacing pistons = not cheap. So while I'm dumping money into this pit. Would it be more cost effective to 1) Try and track down another used engine (it would be the 3rd one in this bike) 2) find gently used juggs and pistons and slap it together. 3) buy a big bore kit and throw that on...

Opinions?
Can some one shine so light on what all this stuff is gonna cost me? It might have to wait a bit as I have my 3rd baby girl coming this november.

[tinman905]

You can find engines as low as $99.00 . Buying jugs and pistons/rings you can find under $50.00 but that's a gamble. A big bore could run up to $800 to a $1000 after machining, gaskets and seals .

[TopCatGr58]

Hey Freak,

The cheapest will be to find a spare engine locally, and just swap it. But looks like as you've found out, you can't guarantee what you'll get!?

Until you tear it down and mic the cylinders, you can't tell how much wear and out of round they are. Depending on the wear, you might be able to get away with a hone, and then new 1st oversize rings filed to fit in the OEM honed cylinders. There was a thread about alternative generic rings and sourcing them vs. the $$$$ Yamaha brand. If too much wear for a modest hone, then a bore is in store...but you can't get regular YAMAHA oversized pistons anymore. Again, threads about generic alternatives there also, search the threads.

The Wiseco big bore's run about $400-500 for a complete set, pistons, rings, wrist pins, keepers, and larger cometic brand head gasket. Depending on machine shops...prices per hole $60-80...mine were $40.00 10 years ago! I did the valve job myself with just lapping, vs. $$ regrinding of valves and seats. Gasket kit of $80.00 will get you all gaskets and valve oil seals, won't need the OEM head gasket though.

When I did my topend, I didn't do the bottom end....no new con or main bearings changes. The engine had and estimated 50K miles on it, but had been working flawlessly until the tranny died, and letting it sit for 10 years=rusting in the cylinders, hence the top end job. I've since put some 16K on it, still running strong, and I don't baby it!

T.C.

[TADracer]

I'm with TC

You cannot guarantee what you will get used. You can probably pick up a set of jugs and pistons from somewhere but they will be an unknown quantity so you will end up having to measure everything anyway to be sure. Sooo, I would get (or borrow) a set of outside micrometers, an inside mic and perhaps a 0-6" caliper, pull the cylinders and measure everything you already have. You might find everything is still in tolerance and just needs some attention to detail.

Personally, I would do a leak down test before I pulled the motor apart to try and identify the exact problem area. Then I would clean everything up well taking care to remove every trace of carbon from the ring grooves. Then do a light deglaze hone on the cylinders since this is probably the minimum you would be working with if you put in new rings and if your old rings are still OK, the hone will not hurt them. You can do this on the work bench with a drill motor and a cylinder hone and just be careful. Then measure the bores front to back and side to side in three places, top, bottom and middle (2.815" to 2.819"). This will tell you if you are out of round or out of spec. Measure piston dimeter so you can get piston/wall clearance (.0016"-.0018") and measure ring gap on the two top rings (no need to measure gap on the oil ring rails). Place the rings into the bores using a piston to level them about 1" or so up from the bottom of the bore. Even if your gap is slightly larger than the spec. (which is .008" to .016") you should still get great compression without going to oversise rings. You can go out to probably .030" on ring gap with no problem on a street motor.

If you can borrow the measureing instruments and cylinder hone you can do all this for little or no cost, except for head and base gaskets. If everything checks out, put it all back together (and break it in again). If not, you are in no worse condition than you are right now.

[freak_leg]

You cannot guarantee what you will get used. You can probably pick up a set of jugs and pistons from somewhere but they will be an unknown quantity so you will end up having to measure everything anyway to be sure. Sooo, I would get (or borrow) a set of outside micrometers, an inside mic and perhaps a 0-6" caliper, pull the cylinders and measure everything you already have. You might find everything is still in tolerance and just needs some attention to detail.

Personally, I would do a leak down test before I pulled the motor apart to try and identify the exact problem area. Then I would clean everything up well taking care to remove every trace of carbon from the ring grooves. Then do a light deglaze hone on the cylinders since this is probably the minimum you would be working with if you put in new rings and if your old rings are still OK, the hone will not hurt them. You can do this on the work bench with a drill motor and a cylinder hone and just be careful. Then measure the bores front to back and side to side in three places, top, bottom and middle (2.815" to 2.819"). This will tell you if you are out of round or out of spec. Measure piston dimeter so you can get piston/wall clearance (.0016"-.0018") and measure ring gap on the two top rings (no need to measure gap on the oil ring rails). Place the rings into the bores using a piston to level them about 1" or so up from the bottom of the bore. Even if your gap is slightly larger than the spec. (which is .008" to .016") you should still get great compression without going to oversise rings. You can go out to probably .030" on ring gap with no problem on a street motor.

If you can borrow the measureing instruments and cylinder hone you can do all this for little or no cost, except for head and base gaskets. If everything checks out, put it all back together (and break it in again). If not, you are in no worse condition than you are right now.

This is going to be step #1 this fall. Tear down and diagnostic. This engine "has low miles" per the PO So I have my fingers crossed that everything checks out and I can just do a hone and re-ring.

The funny thing here is I thought it was already pulling like a monster. Turns out I've only been running on 3/4 of the engine. However I'm really getting tired of the ride for a couple weeks and spend a month on new found issues cycle I find myself in... but on the bright side I should be running out of issues. Right?! Right?! someone throw me a bone here!

[Cobia]

Rebore???

If it helps you...
Just saw a 3mm overbore wiseco kit on ebay for under $600. As you know they're going for over $750 now-a-days. Hope this helps.
Good luck.

[TopCatGr58]

Hey Freak,

I can't recall the details, too many folks and bikes!

If this is a low miles machine, I wouldn't expect this kind of leakage! However, IF it sat for a long time...years, it could have gotten/developed stuck rings!? Since you'll be waiting till winter, you can try something on the next oil change. Put in several ounces of Marvel Mystery Oil, SLOWLY run the engine with a fan blowing, get to close to normal operating temps, but DON'T drive it, you can slightly rev it a little in neutral, but don't put any kind of real load on it. Let it run for 5 minutes or so, then shut it down, let it sit overnight. Then drain oil/change filter, and put in good new oil....duh!

Then ride it and see if it still tends to foul or burn oil!? JAT!
T.C.

[freak_leg]

Hey Freak,

I can't recall the details, too many folks and bikes!

If this is a low miles machine, I wouldn't expect this kind of leakage! However, IF it sat for a long time...years, it could have gotten/developed stuck rings!? Since you'll be waiting till winter, you can try something on the next oil change. Put in several ounces of Marvel Mystery Oil, SLOWLY run the engine with a fan blowing, get to close to normal operating temps, but DON'T drive it, you can slightly rev it a little in neutral, but don't put any kind of real load on it. Let it run for 5 minutes or so, then shut it down, let it sit overnight. Then drain oil/change filter, and put in good new oil....duh!

Then ride it and see if it still tends to foul or burn oil!? JAT!
T.C.

Hmmm I've never heard of Marvel Mystery Oil. Care to shine some light on this stuff for me? As far as miles go I was told that the engine had lower miles on it. I don't have any idea what the PO's owner of "Low miles" is. In the past few years it hasn't sat too much. It kind of got bounced around my circle of friends for a couple years untill I managed to get title in hand for it. (I saw the glory that could be) Regargless in previous years I didn't notice any oil burning to getting blown by so this is a new issue. However I did replace the head this winter. Could the new head cause this? I I haven't had a chance to check the valve shims. Is it possible for the head to be leaking oil threw a poorly shimed valve?

[crazy steve]

...However I did replace the head this winter. Could the new head cause this?..

Yes, it is. If you have bad valve stem seals and/or worn valve guides, either or both can allow the cylinder to suck oil into it, although it's got to be pretty bad if it's fouling the plug. Do you see smoke when you first start the bike? Do you notice oil smoke when deccelerating, or after deccelerating, when you re-open the throttle? These are signs of bad seals/guides. Valve adjustment won't fix this...

'78E original owner

[freak_leg]

Yes, it is. If you have bad valve stem seals and/or worn valve guides, either or both can allow the cylinder to suck oil into it, although it's got to be pretty bad if it's fouling the plug. Do you see smoke when you first start the bike? Do you notice oil smoke when deccelerating, or after deccelerating, when you re-open the throttle? These are signs of bad seals/guides. Valve adjustment won't fix this...

'78E original owner

Hmmm sounds like I'll have to do some reading I've got no clue how to do valve guides, but as with most things on this bike the learning process is half the fun. It does get a little puff of smoke when it first starts. I'm not sure if it smokes when deccelerating... the pipes are behind me (sorry had to be a smart ass there)