mercfocus

iTrader: (3)

Ok, so I have this Hyper 21 that was giving me huge problems a few months ago, so I said "forget it", pumped it full of after run oil and shelfed it for about the last 4 months.

I decided recently to try to resurrect it when I found that Nova Rossi carbs fit it so I got one for a good price and put it on there.

It's now running really good, the temp is totally tunable now and the idle is somewhat tunable too with an exception on start up. It revs really high at first and every once in a while, it just dies. Rippin and running strong but just dies like the LS needle is too lean. I've already experimented with the LS and several tanks. I can not tune this out.

The only 2 issues I have left with this engine: High rev on start up & dying once in a while. (Before, it was a complete basket case: overheating, no power, diying like crazy)

I started suspecting some kind of air leak somewhere else like the front bearing. The 7 x 19 x 6.

I took it all apart and when I turn the crankshaft, I see the inner part of the bearing doesn’t turn with it. I can see little marks on it that sit still while I’m spinning the crank. Is it supposed to do this?

The bearing will spin if I put a little side pressure on it. I also tried this with a Force 28 crank I have and a Nova Rossi bearing I just recently replaced; I don’t see any issue with that. The Nova bearing spins on the F 28 shaft.

So I guess my question is: Is where the bearing sits on the shaft where I'm getting an air leak?

Nitro Tiger

iTrader: (6)

If your a bit suss on the front bearing just change it out, a good quality steel bearing like Tko is not that dear.

And if you want to check if the font bearing is leaking, whilst its running, spray some brake cleaner on the front bearing, if the motor dies your bearing is leaking.

mercfocus

iTrader: (3)

ya, I was looking at the ceramic bearings that are affordable. Just change that one I guess. The main seems fine.

Question about that brake cleaner spray: How do I get it on the bearing with the clutch in the way?

I don't want that stuff inadvertently spraying all over the rest of my car. Especially on the clutch.

2nd question: Could brake cleaner spray be used to check the rest of the crank case for hard to see cracks/leaks?

Nitro Tiger

iTrader: (6)

Just use a tube like what you get with a WD can, that connects to the nozzle. But really just put the can up close to the back of the flywheel a spray, any excess will evaporate anyway.

Possible but unlikley to have any cracks in the crankcase, a tell tail sign of leaking is wetness and dirt buildup around the wet spot, e.g. Ive had a leaking exhaust gasket on the back of the motor, underneath the manifold, it was wet where fuel was leaking out, hence creating a air leak.

3DRCRACER

iTrader: (1)

From what you are describing, you may need a new crank. If you can see marks on the crank where the bearing sits, its probably worn down and a new bearing will probably do the same. Or, the bearing itself is worn or poor quality and just doesn't fit like it should. Try using a caliper and see if the area where the bearing sits on the crank is smaller than the area next to it where the fly wheel sits.

To answer your question, yes. This situation can cause all sorts of issues.