Saving a 1980 750 twin.

Bearing clearances all oil passages and oil pressure.


.

.

Here are the pistons i received from JE. 86mm with 10/1 comp

No eBay APP ID and/or Cert ID defined in Kunena configurationAny tips on determining a good crank on eBay? Looking at this one....

No eBay APP ID and/or Cert ID defined in Kunena configurationI am not sure it's the best choice: someone was meddling with those crankshaft balancing (two fresh drilling marks where should be none).

I also prefer ebay lots with clear description and mileage indicated, even if this features certainly do not guarantee anything.

Here is 1980 crankshaft with connecting rods (which might be a bonus in your situation).



By the way, I ike this custom pistons of yours and I like design of 750 twin engine. Hope one day I would be working on one of them.

I dont want to buy a crank that isnt showing the rod journals, because who knows whats hiding under there. I don't need rods as I managed to score some NOS connecting rods for $50. In doing so I discovered the difference between the early rods (76-79) and the late rods (80-83). Early rods have the small end copper plated, the late model rods do not.

When you say copper plated would that be a small end having a bushing?
I needed a crank for a 440 once. Got one from a bike salvage outfit in Utah thru evil bay.
You might what to try an established business thru evil bay that has a good feedback.


.

The small end is indeed plated. I thought it was a bushing at first but i was able to scratch some of it off in a nn crucial area .

Ive been inspecting the components one by one and the glitter from the bearings is everywhere. its like the aftermath of a stripper party. Its in the transmission bearings, which are available, however it also is in the needle bearings for the balancer as well. Those are unavailable, and reading the manual it states that they should be replaced if removed. The bearing material is quite soft. I'm wondering if it did any long term damage, and if it would it be safe to clean everything extremely well and reassemble the balancer as is.

Also the clutch is well cooked. Maybe I should get a new engine?

DoctoRot wrote: Maybe I should get a new engine?

williamsport.craigslist.org/mpo/d/middle...twin/7056688504.html

After talking to a local engine builder in detail and explaining the application he thinks the balancer bearings are fine. . He told me to clean them with electronics contact cleaner because it has a very low surface tension and blow it out with very high pressure. then shoot WD-40 in there and repeat the process. I have access to a compressor that goes to 150PSI so that will do the trick.

I will reevaluate the bearings after cleaning with the balancer assembly. I really don't want to have to go through the trouble of replacing the bearings. getting one of the bearings out will be very difficult as its in a blind hole and its behind another bearing bore.

further more he thinks that the damage was started by the miss-shift and resulting over rev that I had early on in the engine break-in. Because I went from 7500RPM to 1100 RPM almost instantly it caused the oil pump to cavitation and pump foam into the crank at high RPM causing material loss. he thinks this may have been an ongoing problem because of my oil selection (Motul conventional 10w-40) he told me to look for some anti foaming oil to combat this.

thoughts?

I just saw a show on MT tv about oil foaming. They were using a built Chevy rat motor. With the stock oil pan and the " correct" amount of oil, it was surprising how the oil pressure dropped pretty drastically above 5,000 rpm or so because the oil was so well aeriated. They then installed a Milodon baffled pan, and the oil pressure improved a bit, but drastic gains were made in oil pressure and horsepower as they lowered the oil level so that the crank could not pick it up and fling it around.
Since our bikes have unit construction, I suspect the transmission gears will keep the oil frothed up no matter what we do, so an oil formulated to avoid foaming seems like a good idea.

I watch that episode also. I was really surprised that removing oil and adding windage try would allow so much more HP. I've heard this in the past but have never seen the practical testing to prove it. I've seen scrapers made for the big Kaws maybe they are available for your 750

I also saw that episode! i love that show, they always pick great things to test. I have seen scrapers on KZ1000s. I'm wondering how effective it might be on this engine. Something to look at at closer for sure. I was quite impressed by the power and I'm wondering if adding an oil gate on the pan baffling would be worth it, I have one on my KZ1000. This bike pulled surprisingly hard in the last form and I'm moving to a better power to weight ratio.