Yamaha TRX850 Enthusiasts Forum

I've just had a good look over the top end of the bike and have determined I need a new timing chain and sprockets and also new inlet valves. A few questions....

1. Do the valve seats generally need attention other than lapping when putting new valves in?

2. Have we determined whether the Tsubaki chains are that much better than genuine? Where is the best place in Australia to get them or should I search eBay?

3. I was just quoted $60 ex Sydney each for the valves, anywhere else that does better?

Cheers.

Haven't got to the valve guides yet so there could be more questions.

also, has anyone got a set of over sized pistons they don't want? How much?

1 - shouldn't do

2 - No ( but that's what I fitted last time)

3 - can't help you there

hey i was told by Red Baron in Auckland NZ, $20 each for vavles, and thats from yamaha,
was about a year ago though

Is that $20 South Pacific Peso. That should be about Aus$2

Do you have a contact number for them handy? I'll do a search as well. Might end up stacks cheaper to get them to send them to me.

$20NZ for valves is bl**dy cheap! If you can get them for that much, then go for it! Don't have the receipts handy, but I think I paid $55-60 for them down in melbourne...

The valve seats seem pretty tough, mine just got some minor attention when I had the valves installed, and if you check my post on the rebuild, you'll see how bad the valves were.

How many kms on your bike out of interest?

About 35,000km.

The internals look in pretty good condition. Popped the head last night and oil pump cover. Happy with what I am finding so far other than the amount of carbon in the combustion chamber. I think I'll keep going and check the rings for replacement and measure the bore's, oil pump clearances etc. the caseings look good but the paint on the head and barels is faded, may redo that so it should look tidier. It's a slippy slope now taht I've pulled this much apart, if it wasn't for lack of funds I'd be putting it back together a lot differently ie. bigger pistons, FCR's etc.

I ust keep unbolting things at the moment. I now have the barels off and the pistons on the bench. some more questions.....

1. After 35,000 odd km would I expect to see some honing marks still in the bore where the rings sweep?

2. I haven't done any measuring of the bores yet but if they are within tolerance would a basic home honing with the drill be sufficient to put new rings in?

3. Has there been a consensus on whether the crank needs a rebalance after putting a 878 pistons in? Can I go bigger with the stock sleeves?

4. The timing chain had D.I.D. markings on it. Does this suggest it has been replaced at some point or are the stock chains made by D.I.D. for Yamaha?

Some pictures now. Any comments on what can be seen that are problems? Thanks.

Cylinder 1


Cylinder 2


Piston 1


Piston 2


Gudgeon 1


Gudgeon 2

You might want to check bearings - that sort of wear could be what leads to pistons running in an oval sweep. My best is that they are very slightly out of round so will require a rebore rather than a hone (but you may be lucky)

As for balancing teh crank with JE pistons - there is no NEED to do it but the engine will benefit from having it done

Bugger! I was hoping to not have to check the crank. I suppose if I was doing it properly I should do it anyway.

From the other thread, what does a set of the JE pistons and associated 'bits' cost in the old blighty? Does any of the aussie boys know if there has been/is a local supplier?

devlin wrote:Bugger! I was hoping to not have to check the crank. I suppose if I was doing it properly I should do it anyway.

From the other thread, what does a set of the JE pistons and associated 'bits' cost in the old blighty? Does any of the aussie boys know if there has been/is a local supplier?

IIRC the pistons etc cost about £330 and expect £50 - £70 for the rebore

Thanks phuk.

I spoke to Albion Motorcycles here in Brisbane as they are a JE agent. The condescending prick won't be getting my business.

I may get a set of barrels from ebay uk and get them sent straight to TTS. Then get TTS to post them with pistons to me. Do they have to order 4 from JE or have they got the deal to just get 2. Maybe order the pistons from them and get the rebore done locally. Worse bit is I have absolutely no money to do this. Bah! Might just get the motor back together with new parts where needed and concentrate on the carby, headers, inlet valves and clean up and match port of the head.

I'm down the just the crank case and gear box now. It was interesting getting the motor onto the bench, which is above belly button height. Imagine 'clean and jerk' type of scenario. Better than working on the floor. Very little oil sludge type stuff in the top oil tank. Will pull the sump off tomorrow night after the footy. That's if NSW win. I'll have the shits if they don't

I just bought a pair of pistons from TTS

And yes, the TRX lump is one of teh heaviest motors I have ever come across!

After a bit of digging around I can get 1.0mm oversized pistons locally from Yamaha. That would give me 868cc with std. compression. Which is good as I want to put a Rotrex super charger on it in the near future. Why? Why not? It will be a fun (frustrating?) exercise.

Below are some shots of the crank bearings and journals. The wear marks you cannot feel with the fingers and I haven't done any measurements. I know the photos aren't perfect but does anyone have any comments on whether they look fine and will last or should I get new ones? Everything else inside looks really good. No buildups of sludge of gunk. Not sure what I was expecting in that regard though. My only real concern is the oil pumps. I'll have to do another proper measure of the clearances there as I think they are out of tolerance, but only just.

devlin wrote:Thanks phuk.

I spoke to Albion Motorcycles here in Brisbane as they are a JE agent. The condescending prick won't be getting my business.

I may get a set of barrels from ebay uk and get them sent straight to TTS. Then get TTS to post them with pistons to me. Do they have to order 4 from JE or have they got the deal to just get 2. Maybe order the pistons from them and get the rebore done locally. Worse bit is I have absolutely no money to do this. Bah! Might just get the motor back together with new parts where needed and concentrate on the carby, headers, inlet valves and clean up and match port of the head.

I'm down the just the crank case and gear box now. It was interesting getting the motor onto the bench, which is above belly button height. Imagine 'clean and jerk' type of scenario. Better than working on the floor. Very little oil sludge type stuff in the top oil tank. Will pull the sump off tomorrow night after the footy. That's if NSW win. I'll have the shits if they don't

I forgot to ask? who won?

You'll keep!