JE878 gone bad

[NWS870R]

I've been following this thread for a while now & observing some of the tips/advice that have been offered. I'm not sticking my tongue out at anyone here, but why don't you use genuine Yamaha 868 oversize pistons? No 8K rev ceiling, no mass issues, approx the same gains & no 'going round the houses' to make sure everything else will cope with the extra capacity/mass/lubrication issues? Just my opinion but think it would save you money in both the short & long term?

[cobbadiggabuddyblooo]

+1.. something that went through my mind 6mths ago when I started my rebuild after researching how ,what and why on rebuilding the motor and the components I'm using.
But I'd already purchased an 878 kit and I found it hard to source 1mm OEM oversize pistons here in Oz.
Once you start to play with compression ratios alone, timing and temperature all come into play and to truly find and keep the gains on offer you have to modify other components.
If you don't, the average 2% gain here and there are lost and in some instances you lose more than what you started with so you may as well just utilise the OEM 1mm oversize and just time the motor correctly to get the optimum from it.
Mixture, flow and timing is the key...

[M.V.]

Question came to mind.. If replacing the rods without splitting the cases, how do you torque the rods up when placing back on the crank?? Can you take a couple of photos please on how you manage this as there isn't much room to dance around in there so It would be great to see how this is achieved ..

You would just take the sump off. Right?

[cobbadiggabuddyblooo]

the kiss method.. Looking back thro my photos I found this. I had accessed mine by splitting but I needed the crank out...
10 points to M.V.

[misterdimwiddy]

I've been following this thread for a while now & observing some of the tips/advice that have been offered. I'm not sticking my tongue out at anyone here, but why don't you use genuine Yamaha 868 oversize pistons? No 8K rev ceiling, no mass issues, approx the same gains & no 'going round the houses' to make sure everything else will cope with the extra capacity/mass/lubrication issues? Just my opinion but think it would save you money in both the short & long term?

That is a very sensible perspective on things.

If I was starting from scratch and knew what I now know after 6 years of TRX ownership I would probably go down that route but I am where I am and have invested heavily in my track day machine.

I am not troubled by the issues that I come up against because this is my main passion and my escape from family and work life (2 much loved children who are relentlessly demanding of my time and energy).

There is so much of technical interest out there to satisfy an enquiring mind and I enjoy the research plus having my hands inside an engine is very much what it is all about to me.

This will be my final TRX engine build I think at which point others will no doubt gain from the list of performance parts that will be up for grabs Then I will go shopping for an RC8 or 1290 Superduke.

Before then I have another year of track day fun ahead of me with what should be a reliable motor.

[Tarwetijger]

misterdimwiddy, did you get the con rods out without splitting cases? And with the engine in the frame?

My cilinder head is ready but the guy who took care of it, adviced me to replace the big end bearing shells. I'm not sure how to do this at the moment.

[dandywarhol]

Just been looking at a photo of Tarweijger's JE pistons - surepl there's scope to remove 40g from the gudgeon pin bosses, there's certainly enough metal around them - just make sure the edges are finished with a curve, not right angles and sharp. Cheers for the pic Tar...................

[misterdimwiddy]

I agree. Looking at JE literature online they do custom pistons that remove material from the pin boss and also mill material where the wall thickness is increased below the oil scraper ring. JE comment that this can be done while 'maintaining strength and integrity'. Just leaves post milling heat treatment and potential dimensional change as an unknown.

JE will also do DLC coated pins at about $90ea

The place in Milton Keynes can superfinish (removes about 1 micron thickness) and DLC coat 2 pins for £28 so I am going to do that. Can't find info about tempering temperature of JE pins so they are going to coat a used pin and then measure any effect upon hardness before doing the two new ones. There is a whole world of DLC type coatings and I will have to assume that the company knows there stuff; they do a lot of automotive applications (cams, buckets, pins, valves) so fingers crossed.

Just found this pic of Sarron Suzuka TRX; oil cooler location will be copied from this if my oil temp turns out to be much above 90°C.

If anyone has messed with the original oil hose fittings, can you tell me where I can get various anodised banjo's etc?



The fun goes on...............

[misterdimwiddy]

misterdimwiddy, did you get the con rods out without splitting cases? And with the engine in the frame?

My cylinder head is ready but the guy who took care of it, advised me to replace the big end bearing shells. I'm not sure how to do this at the moment.

The motor was out of the frame. It is awkward getting the rods back in even with the motor upside down on the bench and I would not try it in the frame.

I will post a pic of the 3/8" drive I used to retorque the big end bolts. There is a boss in the crankcase casting within the sump that prevents perfect alignment of the extension onto the rod. I used an extension that allows slight misalignment of the socket from the ratchet extension. In an ideal world I would split the cases again but I can't face removing the generator rotor, balance shafts, clutch etc etc having only done it this spring. Hope this does not come back to haunt me next year

You could argue that by not being exactly aligned the torque applied is not precise but the misalignment is slight and I am willing to take the chance.

After my experience this year I would definitely inspect the big end and main shells before fitting an 878 kit. Peace of mind is worth a few hundred quid on gaskets and shells.

Hope it goes well for you. You will love the results

[Tarwetijger]

The motor was out of the frame. It is awkward getting the rods back in even with the motor upside down on the bench and I would not try it in the frame.

Thanks for your quick reply. I thought so - my engine is still in the frame. Since head and cilinders are easily taken off with the engine in the frame.
But I will have to get it out, it is as you say: peace of mind is what I'm after in this case.
If I don't change the shells right now and things will go wrong, I will be really like

Hope it goes well for you. You will love the results

I think I will.

[alextrx850]

Took the Yamaha 2nd oversize pistons to work today and sat them on the jewellers scales in the paint room.
Piston1 ..324.7 grams
Piston2..324.5 grams
Chris enclosed two sets of gudgeons
First set weighed at between 72.5 and 72.3 grams between the two.
Second set from Chris weighed at 79.3 and 79.9 respective.

Guess I'd use the lighter set of gudgeons pins in a build, wondering to piston weight differences to the JE slugs, and the Yamaha ones.

[Tarwetijger]

The guy who did my cil.head would not believe me, so I also weighed the pistons. With a kitchen scale so not very precise. The JE pistons are 25 gr heavier per piece compared to the original ones.
Genuine piston pins 130 gr (both together) and JE 175 gr.!
He was very surprised that a good brand as JE would come up with such lumpy (cheap?) piston pins, while the pistons are high quality and well thought-out.
I can live with the heavier pistons, but the pins... It is just odd.
The guy even suggested using original ones, despite these are a little shorter. What is the worst that can happen? It is not that the longer ones are a tight fit, there should always be a little play. He reasoned that you just would make the play a little bigger. I understand what he was saying, but I'm not yet totally convinced.
Has anyone looked for other suitable pins, like from another bike? They are not that special, such pins are in every bike.

[Kenny]

whats the weight and length of a pin from the TDM900?

[misterdimwiddy]

Question came to mind.. If replacing the rods without splitting the cases, how do you torque the rods up when placing back on the crank?? Can you take a couple of photos please on how you manage this as there isn't much room to dance around in there so It would be great to see how this is achieved ..

You would just take the sump off. Right?

Photo below of 3/8" socket drive misalignment on the big end bolt that is difficult to access with the cases together. The extension I used allows a low angle of misalignment so that the socket is square to the nut.

[misterdimwiddy]

As I wait for my barrels to be finished I am adding odds and ends to keep an eye on oil pressure and temperature.

Have drilled and tapped the oil tank base at the rear (1/8"BSP) to take a temperature sensor so that I know what the oil temp is doing. This will be switched manually to read either water or oil temp through the standard gauge on the dash.





I am using non aqueous coolant that boils at >180°C, doesn't degrade with time and greatly reduces the chances of local boiling/hot spots near the combustion chamber.

Have removed speedo and replaced it with an oil pressure gauge that uses a remote sensor on the top end feed pipe.



Now I can tell if it is cooking the oil and will plumb in a cooler if needed.