Hi all, I have recently bought a Mk1 in need of an engine rebuild. The bike did come with a spare engine, which appears to be from a later model. I am hoping the cranks are interchangeable because the Mk1 engine's big end is goosed, but luckily the spare engine has a good crank. The clutch side of the cranks are different, but look the same once built up (one has bolt and the other a nut). It looks like I have got some fairly new seals in the spare engine, so I have just ordered 2 new main bearings (63/28 C3) at £11 + Vat each from Antifriction in Wrexham.
I understand that the MK1 and MK2 engines have different ignition timing, and assumably different CDi units. This is why I am not simply throwing the spare engine straight in.
This is my progress so far, once the bottom end is rebuilt with any dodgy bits replaced I will turn my attention the the top end. I have got 2 sets of everything I need and all look in good order and standard. I did measure the piston ring gaps and could do with some new ones. Are they the same as the 66mm TRX250 items?
Anyway I will keep you posted on my progress through the rebuild.
Neil

Welcome Neil.
I would have a word with the bearing supplier as the C3 designation bearings has extra clearance for special application and is not required or desirable for the CRM engine.

neil.

i'm going the opposite way........mk1 bits onto a mk2.2 top end and cases.
my mk1 motor with the exception of the gearbox is good. sadly the gearbox /sprocket decided they would have a bust up and trash the l/h casing.
just waiting on some gaskets, which should be here fridayish before i start.
the mains/piston etc in the 2.2 look ok( limited access i know !) so not intending to split the motor unless i have to.
will advise any oddities.....d

Wheelright has just fitted Mk1 ECU and PV controller and loom onto a Mk2. He had to alter the pick up positions on the generator.

Hi Eddie, thanks for the heads up on the bearings, I have always used C3 spec on cranks without any problems. I've not done a CRM before, is the original part not C3 spec?

Hi Voodokid, It all seems do-able to me. I have noticed that the barrels are slightly different. On the front (exhaust) side the neewer one is more bulky with a threaded plug on one end, which looks like something to do with the powervalve. All gaskets look the same so I can't see it being an issue. Good luck

Hi KnackeredMK1, I see that the Mk2 fires 2 degrees before the Mk1. Therefore i assume it is a simple case of elongating the wholes of the pick up sensor mounts and moving it by 2 degrees. Thanks for the info, I think I will revert to the MK2 motor beacause the crank casings are scored in the Mk1 due to the buggered big end.

mereneil wrote:Hi Eddie, thanks for the heads up on the bearings, I have always used C3 spec on cranks without any problems. I've not done a CRM before, is the original part not C3 spec?

If you have used them before then I guess there is nothing to worry about. The idea of the extra clearance/play with the C3 bearing does not seem right but I do not know that for a fact. I read a thread somewhere that LT had supplied someone with a C3 main bearing by mistake. When I fitted mine I just banged them in without checking

Is Antifriction a good company? I've not heard of them but they are local to me so could be handy.

[quote="Eddie Evans"]If you have used them before then I guess there is nothing to worry about. The idea of the extra clearance/play with the C3 bearing does not seem right but I do not know that for a fact. I read a thread somewhere that LT had supplied someone with a C3 main bearing by mistake. When I fitted mine I just banged them in without checking

Is Antifriction a good company? I've not heard of them but they are local to me so could be handy[/quote]


This is the first time I have used Antifriction, but they are alot cheaper than others, especially with a haggle. I got £5 knocked off all in just by asking.
As for the C3 issue, it depends on your tolerances really. I have had mains go tight once fitted due to how quickly they spin up and get hot rapidly. The extra clearance between the balls and races is taken up by the expansion due to heat. I spoke to a 2 stroke race mechanic about it a few years ago and he said that they are especially important if you want to give the engine some welly straight after the rebuild. I guess that running the engine in softly once it's back togehter helps. It is very common to have the crank spin inside the inner race, or the outer race spinning in the casing due to the bearing being tight, I have come across this and I'm sure a few others have.
The extra clearance is only about 15 microns (15 thousandths of a millimeter)
Food for thought anyway.
I can get a set of normal ones from work. I will experiment fitting both and see how freely the crank spins by hand. Will keep you posted

http://i610.photobucket.com/albums/tt18 ... one128.jpg

http://i610.photobucket.com/albums/tt18 ... one130.jpg

A couple of pics of my bike. Yes it does look sorry for itself at the moment, but it will be flying round the lanes before you know it! I do have all the bits and plenty of spare engine bits.

Good Luck with that project Niel.

I have a project in motion as well.

be very wise around TRX Engine mods,and to be fair you might save a few pounds by using the piston and a diffrent small end.

My ethos after much help from the guys on here,LT only! when you call them everything becomes standard fair, them alone have the best understanding of these CRM imports coupled with parts on the shelf!

Overall LT are 15-20% more than elswear on most bits, but the "service" is AAAA+,The parts for my engine £435 with the crank rebuild,plus the guy completing the re-build local,Bearings and Seal are cheap from grey market sellers and just as good.


Take a good look around this site and you will grab all the will and drive you will ever need.

Tx
Capt

capt wrote:Good Luck with that project Niel.

I have a project in motion as well.

be very wise around TRX Engine mods,and to be fair you might save a few pounds by using the piston and a diffrent small end.

My ethos after much help from the guys on here,LT only! when you call them everything becomes standard fair, them alone have the best understanding of these CRM imports coupled with parts on the shelf!

Overall LT are 15-20% more than elswear on most bits, but the "service" is AAAA+,The parts for my engine £435 with the crank rebuild,plus the guy completing the re-build local,Bearings and Seal are cheap from grey market sellers and just as good.


Take a good look around this site and you will grab all the will and drive you will ever need.

Tx
Capt

A glowing testament, so not all, James Hunts, and A.W. Anchors then!!!
Mike