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
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!
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
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.
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.
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?
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.
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.
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.
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
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
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.
But will have it checked out by a mechanic just to be safe.
So, managed to make a lot of progress, bikes running great, little things that need to be done before my trip coming up in Desember. Aiming for a 5000km round trip so bike needs to be 100%.
Fitted a bashplate, new switchgear, bar risers and LED rear indicators, all working a treat. Things to be done.
New exhaust (being custom made in the next 2 weeks) Fix two oil leaks, one through the neutral switch and the second is the decomp lever plug.
Abit off topic here but currently watching Season 5 of "Itchy Boots" on YouTube and the start of that is in South Africa.
Interesting Watch for we who see bugger all of that part of the World on telly.
If you've got plenty of spare time, like us, during Winter and Covid Lockdowns...... 🙁
Cheers
Kiwijeff
Abit off topic here but currently watching Season 5 of "Itchy Boots" on YouTube and the start of that is in South Africa. Interesting Watch for we who see bugger all of that part of the World on telly. If you've got plenty of spare time, like us, during Winter and Covid Lockdowns...... 🙁 Cheers Kiwijeff
Yeah, been watching her videos the past few weeks, she's currently in Botswana after traveling through South Africa and Namibia.