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Post Info TOPIC: Main bearings


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main bearings
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Hello.

I need to replace the main bearings on my 1994 ttr (4GY), and am wondering whether i need a special puller to remove the flywheel or any other special tools.  Also are the gaskets and oil seals the same for the blue ttr's as i was thinking of ordering them from BOATS, unless any one knows of any better suppliers.  (Headgasket from Brian).  Any help appreciated.

Mike



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Hi Mike

Ideally you need the simple Yamaha flywheel puller but if this is the only TTR engine you are going to take apart it probably isn't worth the investment. You can use instead the rear axle but make sure you screw it in straight!

I can't recall needing any other special tools apart from a device to hold the flywheel when assembling so that the flywheel retaining nut can be done up to the correct torque.

The main bearings come out (and go back) more easily with a bit of heat. Ally expand 3 times (approx) that of steel so should come out a little easier with heat.

Some brief details here http://ttr250.activeboard.com/t43805944/ttr250-fitting-a-325cc-big-bore-kit/

Your gaskets and seals are the same as for later TTRs so you can certainly order from the BOATs fiche. Don't expect to get your order quickly though if they haven't got the parts in stock. Customs at Heathrow can add another 3-5 days depending on whether they get the parcel just before a weekend or not.

AllBalls do a main bearing kit which Steve and I used on our 325 rebuilds - see here

Good luck and don't be shy about asking for help if you need it wink

Brian



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Hi Brian,

thanks for the prompt info.  It is something i will probably get around to later in the year, but at least it will give me time to order the gaskets.

Cheers.

Mike.



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Currently rebuilding an engine and the main bearings are a bit "lumpy". Surfaces have gone grey and there are marks where it looks like swarf has been crushed into the surface. Anyway, I notice a slight difference in the numbers on the bearngs. Both are Koyo 63/28-3, but the left hand one also has SH stamped on the inner race. I know that the whole thing is designed so that the crankshaft stays in the left hand bearing during disassembly, so are the bearings actually different or is the crankshaft machined to different tolerances? Are the bearings different part numbers on the Yamaha parts fiche?

I intend to replace the bearings with more Koyos but that SH doesn't appear when you google 'em. Sorry Steve, just don't have a great deal of faith in Allballs.

Cheers,

Simon.

 



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No worries matey

Here are some numbers for you

No 9

BEARING
9330637807

Replaces 93306-37804
 
No 10
BEARING
93306-37807
Numbers are from fowlers

e96e5e74621377ecd7295b652d157468.png crankshaft.png

Hope that helps

Steve



Thought It would be nice to give Brian a restwinkwink





-- Edited by ttr steve on Sunday 16th of October 2016 06:59:54 PM

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Thanks Steve,
So they're basically now using the same bearing both sides. (NB Looked on Fowlers. On the parts list below the diagram I found, it lists two #10s but no #9?)
Found a pdf on Koyo. It seems the SH refers to "Special Heat treatment", also that the "3" suffix means larger than standard inner diameter. New old stock of the RH bearing is available, but nothing for the special LH one. Odd, you'd think stocks would be paired?
Amazing the things you learn (like all the piston tech I've been researching) when you pull things apart!
Ride safe,
Simon.

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