Short motor needed

[Shire]

Hi everyone. Having a nightmare with my bloody bike at the moment.
I'm looking for a short motor for my @T 2001 model.
The local main dealer said it would work out cheaper that way! To make it worse, my new Trax panniers have just arrived..Arrgghhh..
I knew i should have got a GS!!!

[AlanH]

I thought you had problems with one of the heads? Has it taken out the bottom end too?

[Shire]

Hi AlanH
I'm not quite sure whats happened really. I took it to a main dealer after a local mechanic fitted a rear head and the noise was still there, they said it looked like the front head with camshaft play, so i got hold of another one for the front, now the shop are telling me there is excessive play in the gudgeon pin for the con-rod, i was gutted! The rattle is not that bad but i know its there and i think its getting worse, or it could just be me finally loosing it!

[AlanH]

If the small end has 'picked up', which this sounds like, they could be right that a short motor is the cheapest option. Finding one may be the issue as they are not very common in breakers and fetch a premium amount on eBay if they are healthy.

Small end wear is usually caused by a lubrication system failure of some sort. If you were to start on a rebuild of that motor, you'll probably find other damage. The small end problem may have been caused by debris from the heads or it may just be that the bike has been run low on oil for an extended period which has caused all the problems.

When stuff breaks down such as camchain tensioners, cams, plain bearings in the head etc. , the debris ends up in the sump and often gets sucked up onto the oil pump pick-up screen and partially blocks it. That causes a drop in oil pressure and, if it's metal debris, it's also common for the smallest fragments to pass through the strainer and score the inside of the oil pump housing around the rotors causing a further drop in oil pressure. This in turn can damage other components. The debris gets caught by the oil filter before it's pumped through the engine but it's the loss of pressure that causes the problems.

Assuming your top ends are fine now apart from the small ends, the worst case scenario would require an oil pump, new rods, new gudgeon pins, big end shells (and possibly crank regrind), new mains - and a gasket kit. Best case would be one rod, gudgeon pins, gasket kit. If you did your own spannering it would certainly be a worthwhile repair or at least worthwhile stripping the motor to see what's damaged before deciding on repair or replace.

Bad luck - but even spending out on a new motor you'll still be up on a GS

[Shire]

Hi AlanH

Thanks for the reply, i appreciate it. I've just sent a message to Tony.kai, he's breaking up his 91 Rd04, I was wondering if it would be of any use for bits internally. I know its alot older but would you recommend it?

Shire

[AlanH]

The RD07 ignition system is different so at the very minimum you'd need to swap stuff like the pickups and wiring from your old motor. I'm sure someone has tried this in the past. You'd need to make sure you know the service history of the replacement motor and make sure it's not a case of out of the frying pan and into the fire.

[jaseribbit]

GS? how rude