Knackered Crank?

[fsmlittler]

Two questions for the experts:-
I've just developed a nasty rattle on my Mugello kitted Indian Gp150 that sounds to my untrained ears like big end. Scooter starts and runs fine but the rattle kicks in above 5000rpm. When I put the kit on a few people told me the standard crank wouldn't last long and maybe they were right. Are there any obvious easy checks short of a full engine strip?
Assuming it is a crank/bearing fault what crank and rod would people recommend and is there anything else I should do whilst it's in bits?
I'm running a 26 dellorto and big bore box pipe.

Any advise will be much appreciated.

Chris

[paulmgreen]

Standard crank on a kitted engine is folly!!

Change crank, main bearings, oil seals, reset and strobe ignition when rebuilding . New pistons, rings and all gaskets . Whilst its apart change the clutch plates.

[fsmlittler]

I've read that the Indian GP crank is fine but if I have got to replace it what should I go for? The current set up only seems to rev to 8000rpm.

Is there any check for crank damage before complete stripdown?

Thanks

[Rich_T]

If you have a rumbling or clanking/knocking noise then you have to strip the top end. If you have an untrained ear or are inexperienced in this then you need to take it to someone who knows.

One way to feel how much wear is in the bearings is to remove the spark plug and fan cowling, feel the top of the piston at TDC with a small screw driver then lightly turn the crank each way until you feel the piston move. The amount of radial movement between the two points where the piston moves is proportional to the combined wear in the big and small end bearings. Off the top of my head a run in engine has about 8-10mm of backlash.

This will not check main bearing wear and is generally a 5 second test I do during a full strip down to very quickly assess the crank condition.

If you don't understand this from the description then take it to a dealer, if they hear something abnormal you're looking at an exploratory top end investigation at least. The cost of this would easily outweigh the cost of fitting new bearings, seals and a good crank, cosequently the moral of the story is RTFM and listen to what the kit manufacturers tell you.

An Indian crank is NOT a good ideal. The webs are good BUT the business end (the big end bearing) has a record of being highly suspect. Typically these cranks are about £65-£70 compared to a MUCH better quality MEC crank for £120.

You have an opportunity to learn from your previous corner cutting mistake and luckily, it would appear, that your kit is still OK. I'd strongly suggest you break it down and fit all new GOOD QUALITY parts so you have a known datum and put it down to experience.

[markd232]

Might want to think about sending your indian crank to someone like Harry Barlow at pro porting and get a new big end and conrod fitted (will also shim, balance and weld it about £80) then just new top end bearing and seal kit. Re set timing and strobe to check.

[fsmlittler]

Just started the stripdown and there is approximately 18mm of movement measured around the flywheel at TDC which seems excessive.

[stesjh]

I'm running a MEC crank in my TS1 and have had a trouble free couple of thousand miles now - touch wood!

[Rich_T]

Just started the stripdown and there is approximately 18mm of movement measured around the flywheel at TDC which seems excessive.

You are definately into a top end strip. Out of interest, have you had the fuel tank shot blast or cleaned out in some way recently? The 18mm of play will be in a combination of big end, small end, and wrist pin/piston. I once saw some exceptional wear caused to the wrist pin because of a very fine abrasive residue from blasting (a topic that is well covered here so look it up and hence my question).

You will have to write this off as a learning experience. If you have not changed the bearings and seals now is the time to do that too.