trouble...

Hi,
I removed the jugs on the 650 to fix an oil leak, and when I lifted it, sand that was trapped in between, fell into the crankcase. I am hoping this isn't cause for a complete tear-down...any words of encouragement?

hmm, I'd tear it down myself, I don't know what anybody else would recommend. My issue would be whether it got in the crank journals or in the con rod journals.

I would just pull the oil drain plug and drain the oil, then spray the crank and everything else down with a liberal amount brake cleaner. Lt all that drain out, then flush it once more with fresh gas or kero... then button it back up and put fresh oil in and ride the crap out of it.

Whoah, thats a terrible idea. Then you have no lubrication whatsoever during start up. Theres a good reason why we use assembly lube when building engines. Never spray brake cleaner on assembled engine parts, you'll gall everything so bad on startup its not even funny. FRIIIIICTION!!!

I would drop the oil pan and do a good rinse from above. You can hose with a can of carburetor cleaner and then rinse generously with mineral spirits or a similar solvent.

I think dropping the oil pan to clean is a must on any major engine work to be able to rinse off the sludge layer you will find in the pan. You can also clean the garbage out of the oil pump screen.

IMPORTANT:

To clear out the solvent and prime the engine with oil before running, I would put in a decent motor oil and do a manual pump using the kickstarter. Pump it until your arm is dead and then drain it and fill with premium oil.

I guess if you soaked everything in oil afterwards for a long long time and recirced it up around a few times it'd be ok. Make sure you rotate it yourself a few times too to work in the oil. But make sure you take the clutch apart and oil each surface on re-assembly. You might think you never got any solvent on it but be careful, you could blow apart/warp your clutch plates that way. You can never be too careful wiht this.

thanks for all the input...to be honest, I'm in denial right now:S ...I can't believe I did a bonehead move by not checking for crap in there.:blush:
I DON"T want to tear it down, so I'm liking the idea of dropping the oil pan and cleaning it that way.
The top is completely off, so rotating it by hand for lubrication will be no problem
As far as the clutch, it could use a good freshening anyway as it was slipping in 2nd and 3rd last fall. So this might be a good time to check the plates...

Sounds like a good plan. I might sounds a little crazy but I just don't want to see you post in a little while with a ruined engine.

If I pick up another engine, I might be selling my 650 engine if you need a spare . Nothing for sure yet though so be careful what you do.

I decided to go ahead and do a complete tear-down on the engine. I really didn't feel comfortable doing a rinse.
Since it's tore down this far, I'm going to replace the drive chain, cam chain and guides, clutch plates, and also I want to beef it up a bit.
Should I just go with oversize, or would bumping it up with 750 parts be a good way to go? If I go with the 750, what parts will I need?
Any input is appreciated...

You could swap in a complete (bolt in) 750 motor or install 750 jugs which will allow keeping stock 9.5 compression, 750 head (year depends on which type of timing chain your running) which has slightly larger valves along with the 750 cams which have slightly more lift and duration. It's the same as swapping in a 750 as the 650 and 750 both use the same bottom end. You could also keep your head and just use 750 cams. Decisions, desisions.....

Bluemeanie wrote:

You could swap in a complete (bolt in) 750 motor or install 750 jugs which will allow keeping stock 9.5 compression, 750 head (year depends on which type of timing chain your running) which has slightly larger valves along with the 750 cams which have slightly more lift and duration. It's the same as swapping in a 750 as the 650 and 750 both use the same bottom end. You could also keep your head and just use 750 cams. Decisions, desisions.....

How much would I gain by going with the 750 cams?