Restoring compression and where to get bits these days?

[Snod Blatter]

Hello all, long time no see. I'll post my progress on this whether you like it or not, but hopefully some of you can help me out along the way. Back in September I was happily riding around the Eifel region of Germany when I started to hear quite a loud tap being bounced back at me off the road when cornering, then a few miles later while doing about 50MPH in 4th gear uphill the bike started to slow down and I'm told quite a lot of smoke came out the exhaust. I pulled into a petrol station a few miles later and the bike sounded terrible running on one cylinder. I limped it back to the hotel and found that it seemed a lot better above 4K RPM, and at 5.5K it seemed relatively smooth. Thankfully it was the end of the holiday and, after it coughed into life on Saturday morning, I rode it all the way home to Worksop in the UK on motorways where it seemed somewhat happy. The Eurotunnel was an interesting experience but at least it got up the ramp at the exit!

I hoped it would be something simple like a hole in a carb diaphragm but they seem fine, although the plastic slides certainly rattle around in the carbs now. Finally today it was warm and dry enough to take the head off and.. well..



This is a replacement head from a TDM850 and I'm not sure what miles it has done, but I still find this a very weird failure. I've never heard of this happening on these engines before? I still have the original head with soft inlets, I may choose to replace all the inlets in that but at £60 each they aren't cheap at all. I may remove this valve and see what the seat looks like. I may just get another TDM head and use that. Not sure yet.

Thankfully the bores seem to be fine though she really chews through oil on the motorway:



The hone marks are still mostly visible though the thrust side is glazed with some small vertical scratches on the left bore. I would like to fit OEM 1.0mm oversize pistons and rings but I see these are basically unobtainable nowadays, only 0.5mm items remain and that's at CMSNL so just a few boxes of new old stock. Does anyone have any leads on finding 1.0mm items? Anywhere in the world is fine, I can wait for shipping. I'm not really interested in aftermarket high compression slappy forged jobbies, this is a road machine.

So yeah, this is where I am with it now. I'll try and measure the bores to see if 0.5mm oversize is enough, and keep an eye out for some reasonably priced inlet valves but I doubt I'll find them any cheaper. The cam caps are also a little torn up on this head so I'm not sad to give up on it. Also if anyone has a personal recommendation for getting a rebore done in the UK then let me know, I've never had to do that so far. The closer to Worksop the better, obviously!

[HolerTogni]

Hi Snod Blatter!

Sorry to here that your TRX doesn't run as good as she used to.

Unluckily for you (but luckily for me) I'm not that experienced in reading valve heads or piston heads.
But they really seem to have too much residue on them - carbon (the valves) and oil (the pistons).

And out of interest:
What colour was the smoke when she started to slow down uphill - blue (= oil), black (= fuel) or white (= water)?

Hope you find the parts needed - I'll do some search, also will ask in the German forum.

Investigating greets from Munich!

[Snod Blatter]

Cheers Holer!

They pistons do indeed have a lot of carbon on them but it is still soft, I have actually wiped a lot of it away with a paper towel and scraped the last bit off with my nail. I haven't tried this with the head but I can see if it's crispy if you'd like. On one hand I'm surprised by the amount of build up because the week away in Germany is, shall we say, "sporty" at times. But on the other hand she drinks oil on the motorway and that was the last thing she did so not that surprised really. When the oil is worn thin it can empty the sight glass in about 150 miles when sat at a steady 70, though I never knew if this is being burnt or just blown out the breather - I suspect a bit of both. It got worse over the years for sure. When running around the countryside I only have to top the oil up every 400-500 miles, still awful by modern standards (the rest of the guys find it hilarious) but quite manageable. I last changed the emulsion tubes about 18500 miles ago, I know she's a bit rich now but it's not terrible - still getting 50 to 55MPG on a run, just smells rich. The coolant came out looking fine, I don't suspect any mixing of water and anything else. The radiator was also still full to the top.

As far as I know the smoke was grey, and the loss of power was instant.

Looking on CMSNL again I see the 0.5mm oversize pistons are also sold out, only rings available. I'm sure that wasn't the case just a few days ago! So I'm completely stuck now, unless by some miracle the bores are fine and just need a hone. I can't imagine that with 53K on it.

Also if anyone knows a cheaper OEM head gasket than £89 I'm all ears. Also looking for experiences with the Athena gasket that seems to be cheaper, is it the same just without the special Yamaha sticker on it or are they a definite avoid?

[HolerTogni]

Hi Snod Blatter!

A quick search at a (in Germany / Bavaria) well-known engine repair shop has revealed that it has the parts in stock you are looking for:
https://www.scheuerlein-motorentechnik. ... rmass-1-00

Hope this helps - greets from Munich!

PS:
From memory, Athena gaskets have a bad reputation in the German forum.

[Snod Blatter]

What a great find! Do you know if anyone on the German forum has tried them? I like that the pistons can come with moly coating but they don't seem to offer any further information about them such as whether they are cast or forged, hypereutectic, whether they are guaranteed to weigh the same as OEM and generally any other info. I like that they mention the compression rings are convex though, from what I've read (mostly on this forum!) that is important because the piston rocks in the bore at TDC and square section rings will just score everything instead.

I also like that they offer a rebore service, if they are known to be good then I'd probably mail the cylinders to them. Who better to bore the cylinders than the people who supply the pistons??

Oh and I bought a genuine head gasket, thanks for that

[HolerTogni]

Hi Snod Blatter!

From the few people in the German forum who have own experiences with Scheuerlein, I could find no complaints.

In this connection, already at this time be reminded of the things to watch when reassembling the cylinder head if you need to - just came into my mind.

As to the questions you have regarding the pistons, maybe just write them an e-mail?
I suppose, (at least) someone there should be able to read and write English - and if not, I'll be the middleman.

Offered greets from Munich!