98 787 Cylinder (jug) needed

[jamin690]

All, I have had to rebuild one engine in my 98 speedster now for the second time due to a oil pump that was going going...gone. In both instances of failure, the engine siezed. Now that I have honed the cylinder out a second time and put everything back together, there is oil collecting in one of the jugs (the one that needed the most hone work both times). My buddy and I have concluded that we may have honed out the jug a little too much for this NEW piston and rings and its now allowing oil past the rings.

I think I am in need of another jug for this but I am not willing at this point to buy a brand new one. the part number for the jug I have is 290923503 - 420923503. I am trying to figure out if there are any other years that I can get the 787 jug from and have it work properly. I see many ads for rebuild kits that state one 787 jug works for all of them, but then they don't cover my specific part number.

Any help with this, as always, is greatly appreciated.

 

[timmyboy76]

think you need a new crank. The inner seals leak'n. Empty/vacuum it out, than mark the oil tank, then check it after while.

 

[jamin690]

I'm not sure if I understand why a new crank or seals would be needed. the crankcase always has oil free standing and available to the touch as soon as you take the jugs off. Thats why I am not sure what seals are suppose to prevent it from entering the cylinder on top of the piston.

 

[scooper77515]

I am not the engine expert that Timmy is, so work that out with him.

Now, buying PARTS is my specialty!!!

Always check ebay first. All 787 parts should interchange. It is like having a 5.0 ford. all the same parts (except for where you hook up to the tranny and frame.)

I bought a couple of parts off ebay after looking around and seeing how expensive they were new or from the dealer. Was looking at a manifold for mine and I don't remember what the price was, but it was something over $100. Found it on ebay for $7 or $12 or something. Another $10 or so for shipping.

Discuss with Timmy before assuming you need the part, though...he is pretty knowledgeable about what he is talking about.

 

[timmyboy76]

:redface:, oh gosh, stop it...:rofl:

There should be no oil in the "journal" area, chief. The bottom end gets its oil, when its injected or premixed with gas. If theres a standing oil bath down there, then most case, its because the inner seals are leak'n, which the oil there, is from the RV assy. Those inner seals, help keep the oil in that cavity (rv assy).

 

[Chester]

I'm not sure if I understand why a new crank or seals would be needed. the crankcase always has oil free standing and available to the touch as soon as you take the jugs off. Thats why I am not sure what seals are suppose to prevent it from entering the cylinder on top of the piston.

I agree with timmyboy76.
There should not be any "oil free standing and available to the touch as soon as you take the jugs off". You will have to press apart the crankshaft to replace the seals. When working properly, the crankshaft does not sit in any oil.
When you honed the cylinder, how much piston to cylinder wall clearance did you end up with? Leaking piston rings will not cause excess oil to be burned on a 2-stroke engine.

Chester

 

[jamin690]

I see.... That may be my problem with the oil then. The case was emptied of oil when I removed the engine this past rebuild, I was certainly under the impression that oil was suppose to be filled in the case before putting it back together. I will remove that oil and see if it stops the oil from pooling on that piston. Hopefully I do not have the seal problems, It never caused any issue before now but I never had to remove any oil or replace it.

thanks for the info all, Timmy, I had no idea....hopefully I caused this issue and the seals are fine and no damage was caused.