Selecting main- and crank bearing-sizes

HansJ · Post by **HansJ** » Tue Mar 06, 2007 12:08 am

My Rex is in smaller pieces than ever before. I am about to renew the bearings, just as a precaution. I think I have figured out the crank-bearing sizes, based on the workshop manual and the numbers on the rods and on the crank. The main bearings should not be more difficult, unless... Check the picture. It's taken from the rear of the engine, the only place I could find any numbers resembling what was in the manual. There are not only one row with 3 figures, what can I make out of this?

It does not really look professionally made either...

Greg · Post by **Greg** » Tue Mar 06, 2007 10:36 am

Hans...

Mine is exactly the same - in the end I 'postponed' the rebuild and just fixed the old motor instead...

Try Yamaha's tech desk at the HQ for where you are - I've always found them to be more than willing to help anyone with a TRX. The last guy I spoke to described them as 'the thinking man's R1' ... well, we ALL know that's true - don't we?

G

Post by **Max** » Tue Mar 06, 2007 10:42 am

I'm pretty sure the marks are scribed in on the assembly line with a hand engraver, that's why they don't look too "professional" and are usually somewhere hard to see unless you drop the engine out.

Also, did you check your old bearings for color coding bands of paint left on them? Mine still had some marks but since they looked good and were well within tolerance I didn't replace them.

HansJ · Post by **HansJ** » Tue Mar 06, 2007 10:57 am

Thanks guys for Your support. I have not taken the bearings out, so I might be lucky in finding the colour coding on the backside of them... The crank looks good, but two of the lower main shells had small scratches in them. As I am picking everything apart, I thought it'd be better to be safe than sorry, so I'll replace them, then I know for sure the engine is sound (if I manage to put it all together in the correct way...)

I guess I was a bit unclear as usual. The manual says there should be 3 figures only, but as You can see I have 3 rows, and two of them with 3 figures in each. Which should I trust, a fair guess would be the lowest, but guessing is not really an option. Unless I can find out a proper reason for having two groups of figures, I'll probably order according to the lowest, and confirm with Plastigage, and hope I won't have to order new...

Post by **Max** » Tue Mar 06, 2007 11:52 am

Hopefully you will find some color code on them. Tell me the model year and I can give you part numbers off the Japanese Yamaha parts list.

Possible colors are...

Pink
Red
Black
Yellow
Blue
Green
Brown

HansJ · Post by **HansJ** » Thu Mar 08, 2007 8:26 am

Thanks Max! I have the workshop manual with the colour codes. I checked the bearings yesterday. Only one had any remains of colour left, and it was the middle bearing that looked like red. Hard to tell though, could as well be a dark pink...

I am guessing that the number 677 is the one to use, as the other contains a 1, and this would mean I would need a bearing sized 0, and there's none size 0 listed.

The 7 also correlates with the red colour, but here's what I don't get...

Using the formula in the manual (subtracting the 1 at the crank from the 7 at the housing) gives a 6, i.e. one size smaller than the current 7. Using this method will result in at least one size smaller bearing for each exchange, and when the crank is marked with a larger number it will be even more?

Quan-Time · Post by **Quan-Time** » Fri Mar 09, 2007 6:45 am

Just on this,, anyone ever re-ground their crank and put in new bearings to suit ?

Ive heard of many ppl doing this... basically just a "rebalance and regrind" to make sure its all perfect stroke and stuff...

I know cars do it basically on "big" rebuilds.. but never done it on a bike,, altho ive heard of it being done if someone cooks an engine off (low oil / over heat) they de-temper the crank, regrind it, re-harden it..
I suspect that owuld cost mucho monies tho...

HansJ · Post by **HansJ** » Mon Mar 19, 2007 7:23 pm

I think I was right in my assumptions above. Only, one bearing was a wee bit on the tight side. Although within the limits, my engine tuner advised me to select the next bigger bearing. So today I called the Yam shop to order one. They couldn't tell me which colour that would match the next bigger in size, and not even what the difference would be in sizes. They even called Yamaha Sweden... I checked the workshop manual,and it only refers to colours. BTW, it is the bigend conrod bearing, but if someone knows the same info for main bearings, I guess it could be useful for later use.

Not that it will help me right now, as someone broke in to my car and stole all my tools, plus the crankshaft... Anyone see a junkie walking around with something heavy in the pocket, knock him down and give me a ring...
one who knows this?

HolerTogni · Post by **HolerTogni** » Tue Mar 20, 2007 11:24 am

What the fuk ... some Ãƒâ€šÃ‚Â§/%&""$ stole your tools and your crankshaft?!!?!!!

It is unbelievable what some blokes have in their minds - if anything ...

I hope very much that you get back your belongings - though I doubt there will be a great chance therefor ...

Any chance an insurance will pay?

Good luck, Hans

burty · Post by **burty** » Tue Mar 20, 2007 12:51 pm

Bastards! What good is a crankshaft for a theif?

HansJ · Post by **HansJ** » Tue Mar 20, 2007 8:02 pm

Thanks for the sympathy guys. Yeah, the tools I can understand (although not visible from outside, bloody stupid to leave them in the car, but it was late Friday after some hours in the garage, and the Mrs had some opinions about quality time...). The crank had just been checked against the new bearings with Plastigage, and a new or used crank will probably mean new bearings as well, plus the hassle, plus the fact good used cranks don't grow on trees. A new costs ca 800 Euros. The bastards even took a small paper bag with nuts and bolts I broke when taking the engine apart, plus the new nuts and bolts I had ordered. The fact I now have to put the engine together, until there' a bolt or nut missing, ordering it, fetching it makes me go nuts. W*nkers!

Anyone knows of a decent crank lying around, give me a shout!

And no, the car insurance does not cover loose items not belonging to the car, my home insurance would have covered it if it wasn't for the fact the car was parked outside the flat. Grrrr...