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Good day from sunny South Africa
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Good day fellow TTR's

 

Just took ownership of a TTR 250 that has seen much better days. 

Bought as a non runner and after checking compression it was time to open the engine. 

Piston and rings are shot and there is some play on the connecting rod. Need to replace everything. 

Parts in SA are not readily available, so will have to import some parts from Japan. 

Looking forward to some good info from this forum! 

Stay safe 👍



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Welcome to the forum Francois.

Instead of buying replacements from Japan why not try this Clicky Link > ttr Steve on this forum?

You have a wealth of knowledge at your fingertips on ths site too. smilesmile

Good luck and Happy New Year.

Martyn



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Budleigh Salterton. Devon



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Thank you @Cubber

Will keep TTR Steve in mind next time I need some parts! biggrin

Happy new year! 



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Welcome to the forum Francois!

Steve has a good stock of used parts (see here) including crankshafts etc that could save you a lot of money wink

Brian



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Welcome!

I may be wrong but suspect that the TTR250 was not a big seller into private hands in SA.

Have been told that the police and military were big into them though, so some available here may have seen some rough usage.

The one I found is in pretty good shape, does need to have all the (rusty) spokes replaced as it came from the east coast.

From Port Shepstone, a little way south of Durban. It now lives in the much drier central SA - Bloemfontein. Not really central but 500Km from the coast

Barrie.

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Sweet!! If there is anything that Steve can't get for you let me know. I can probably find it here (I live in Japan).

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Morning all

Thank you for all the information and assistance!

So, we started tearing the motor apart and got to something that is quite concerning, the crankshaft main bearing has started spinning in the casing...
Is there some way that this can be saved or will a new casing be required? I am going to get a new bearing to see if only the bearing has worn out, but if the casing has some wear on it, the only solution we can get to is machining very little material out and going one size larger bearing...

Any help or ideas will be greatly appreciated!!
Thanks!

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SaTTR wrote:

So, we started tearing the motor apart and got to something that is quite concerning, the crankshaft main bearing has started spinning in the casing...
Is there some way that this can be saved or will a new casing be required? I am going to get a new bearing to see if only the bearing has worn out, but if the casing has some wear on it, the only solution we can get to is machining very little material out and going one size larger bearing...

Any help or ideas will be greatly appreciated!!
Thanks!


Wow - that's a first on this forum and we have been going for manu years! Bad luck cry

So at some stage the bearing had seized or a large bit of swarf got into it to jam it up.

Which side was damaged and is there any other damage that you can see?

It is worth investigating the use of Loctite bearing fit if the wear is within the specification of their product - see here 

I would imagine that machining the crankcase to take a bearing with a larger OD (if such a bearing is avaialble) or to sleeve it would be expensive.

It might be worth starting with another crankcase half or pair such as here

Brian



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Thanks for the info Brian.

Think it might have been caused by one of the dowels keeping the cylinder aligned being dropped into the engine. Don't think the previous mechanic might have been the best person for whatever job they were trying to accomplish.

Fortunately I have some friends that can machine the case to allow a bigger diameter bearing, my question regarding that is, will that be safe for the casing?

Will investigate the Locktite option aswell, will be getting a new bearing tommorow to see if it still fits into the casing as easily as the one we took out.

If none of these options work or is a viable solution, my next move will have to be some different casings.

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Using a dot punch/center punch at even spacings all round the bearing housing surface will tighten the fit as the dot creates a "crater" shape with raised sides. That, plus Loctite bearing fit should work fine, but long term I think the only way you will have confidence in the motor will be with new cases or a bigger bearing.

Alternatively, could your machinist get the housing built up with TiG weld and remachined?

Good luck!

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Thanks Mossproof

Some of my mechanic mates made the same suggestion, I have bought Loctite as extra insurance, but as you mentioned as well, to ensure confidence in the engine long term new casings would be the better option. 

 

Unfortunately a larger bearing is not an option, local suppliers do not have anything available. 

 

Another option would be to machine the seat and have a sleeve made to fit and allow for the standard bearing to be re-used.

 

Got a new standard size bearing to see if it might fit tighter, but no luck, it goes in just as easily. no



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The casing 



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Plenty of room for a sleeve/ring shim there (is there enough thickness the other side of those retaining stops?) and prob a good option if he's a milling machine meister! The dot punch method does work. Done plenty of old Honda camshaft bearing seats, but the high load on a main bearing would warrant a lot of dots I think.

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Wonder if you can get a "speedy sleeve" to suit, they are a thin shim to improve the sealing area on a worn shaft seal surface

Cheers Terry

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It seems that other than new casings a sleeve or the punch method (would prefer the sleeve method) would be the only options.
The new bearing purchased also goes in way to easily.

Think I might check of we can get a 'Speedi sleeve' here in SA.

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Coke cans are very thin wink



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Haha! I only have beer cans available... evileyebiggrinbiggrin



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Managed to get a machinist to machine out the casing and add a sleeve in to fit the standard size bearing. 

Both press fit into the casing, so shouldn't have any issues. 

Hoping it does the job 👍



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Good stuff

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Finally made some progress, only to hit a speedbump...

Exhaust valve lifter bucket has some wear to it and will need replacement, seems like the gap was to big and caused the lifter to wear rather badly. 
Is there another Yamaha model that uses the same valve lifter (part no 9 on image below)?

 



-- Edited by SaTTR on Wednesday 28th of April 2021 09:55:51 AM

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Hi Francois

It is always worth searching on the part number which is 1WG-12153-21

It seems that a few other Yamaha models use the same cam bucket - see here - but the price of a new one seems exorbitant!  

If the hardened steel bucket is worn then my guess is that the aluminium surface that it runs in will be worse?

Brian 

 

 



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Thanks Brian Just received a list of models that uses the same lifters from my local Yamie dealership. The OEM buckets are extremely expensive and have to be order from Japan to get to SA no So I will try and source some second hand buckets local. The cam does have some wear on it, but funnily enough, not as much as to warrant a replacement. confuse But will have it checked out by a mechanic just to be safe.

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