JE878 gone bad

[Tarwetijger]

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

Exactly what I would like to know.

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.

More gauges and lights are always a good thing
I have such an extension for the rachet too, so that will be alright.


Any thoughts on the piston pin story?

[cobbadiggabuddyblooo]

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.

Get yourself a quote to just balance the weight . $200 / 110£ in your lingo and I'm getting the pistons, pins and crank dynamically balanced so I'm sure for the price of new pins you could get the pistons and pins static balanced to the std weights.. If you get the weights back to std your taking the excess stress away once again so there shouldn't be issues .. Then just look at timing as you will prob need to retard the ignition a little due to the higher compression, once again taking away excess stress and if your air/fuel is within 12-13 your once again maintaining a balance to reduce stress..

[misterdimwiddy]

Think I have read here that TDM900 pins are larger OD than the TRX (21mm?).

JE do pins in at least 4 different wall thicknesses.

My thinking is that the wall is thick in this case to avoid pin section distortion (and associated small end lubrication issues) in a big high comp twin so I am not touching them.

My 40g weight loss is coming from inside the piston below the oil ring location (what JE call a 'window mill') and around the pin boss.

[dandywarhol]

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

900 pins different diameter.

[Kenny]

The thing Im getting at is whats the weight of the 900 pins this will give you some idea as to whether you can run the std 850 pins safely on the JE pistons

[cobbadiggabuddyblooo]

Waste of time with coating the pin as the rod will always be softer than the pin anyhow in whatever format you go...
There always has to be a sacrifical.
Have you contacted JE about the weight of the pin and your concerns???

Ever thought why the weight difference to start?
Because they are a generic piston casting to fit a lot of options and motor configurations within the dimentional specs of the TRX motor and not purely designed for a TRX only.

If oil temperature is your concern ,why not simply do something about the heat to start. (ceramic coating the combustion chamber, valves and top of the piston) will cost no more than setting up a temp sender,guage and oil cooler.
You will have real gains by pushing all that heat straight out the exhaust instead of having it absorbed by the motor to sink the heat.
With less heat absorbed by the motor this allows for cooler fuel to enter the chamber and all the gains here have been explained before about how combustion works within the motor...

Why not just stick to the source of your problem and simply rectify that instead of bandaid metheods to deal with the problem once it manifests itself..

[misterdimwiddy]

I like to think there is not just one correct approach Cobba; there is a saying here that 'there is more than one way to skin a cat'........

I am certain we will both get to our desired end result but perhaps following different routes

[cobbadiggabuddyblooo]

One last observation for all to note.. Please work out your new torque calculations if you choose to attempt to tighten the conrods inplace with a spanner not square to the nut... Cheers .. Good luck and merry Xmas... I won't go in to the physics of it all...

[Rod.s]

One last observation for all to note.. Please work out your new torque calculations if you choose to attempt to tighten the conrods inplace with a spanner not square to the nut... Cheers .. Good luck and merry Xmas... I won't go in to the physics of it all...

This should help…

http://www.specialpatrolgroup.co.uk/spo ... orque.html

[NWS870R]

One last observation for all to note.. Please work out your new torque calculations if you choose to attempt to tighten the conrods inplace with a spanner not square to the nut... Cheers .. Good luck and merry Xmas... I won't go in to the physics of it all...

not just me then Cobba?

The issue with JE pistons isn't really the weight of the pins either, it's the weight/mass of the pistons themselves - hence my previous post. I'd be cautious about removing ANY material from an aftermarket piston personally but i'd gladly be proven wrong?

[alextrx850]

Someone from the side line asking a question,..how come that the venerable JE would produce a piston kit that would throw out the balance.
Surely the replacement piston apart from original would need to be very close to the OEM weight..especially to the calculations of the speeding mass.
Thinking to go for a fast run with a sports sneaker on one foot and a CLOG on the other.

[dandywarhol]

Someone from the side line asking a question,..how come that the venerable JE would produce a piston kit that would throw out the balance.
Surely the replacement piston apart from original would need to be very close to the OEM weight..especially to the calculations of the speeding mass.
Thinking to go for a fast run with a sports sneaker on one foot and a CLOG on the other.

Because the pistons aren't just for a TRX?

I've removed metal from many race pistons when blueprinting and never had a failure from lightening them - maybe I was lucky

[cobbadiggabuddyblooo]

Rod and I researched this over 6mths ago when I first pulled the original std TRX pistons out of the motor and noticed the difference in piston design.
Rod raised the question on design and oil feed and ultimately weight so after hrs and hrs of questioning JE and other engineering faternities. I found my answers.
The JE piston is not specificlly designed just for a TRX.
As I mentioned earier they are an off the shelf forged piston that meet the dimentional requirements and to fit the TRX and a number of other motors .
The TRX have a side relief design on the piston to lessen friction and weight but when costs enter into things, it's cheaper to utilise this generic JE piston than to specificlly design ones for a motorcycle will not sell and have them walk out the door every day. It all comes down to the economics to JE and good business sense in their eyes.
And the weight comes with the specs with your pistons so it's your choice to staticlly balance things back to 0.

This is the reason I've someone to initiate this for me who does nothing but balance cranks,rods and pistons and has done this since day dot and balanced more JE pistons than I've had hot dinners.
This simple task takes all the extra stress this will cause out of the equation (apart from the forces with higher compression) .
The extra piston skirting does add to wear factors a little and friction but thats the nature of the beast with this design.(there's nothing wrong with this design as such just there is better..)
I've placed numerous links and pages of information that I have had the pleasure of being mentored through my rebuild by some of the best engineers, professional race mechanics , championship races and builders who luckily for me have blessed me with their knowleage and experience as they have appreciated the extent to which I have taken to create a motor that will take advantage of these hundreds of combined years of expreience.
And ultimately the principal is simple.
Tuning each part of the motor to get the most from what is on offer and compliment each part to enhance each other.
And balancing the pistons is the first part to compliment the flowing and cam timing to what these are tuned to .
As it all starts at the input side of things..

Even if you don't go to extents of flowing your head or changing cam timing or valves on your rebuild with JE 878 pistons, this should still be at least one basic step you should try to initiate to stop yourself from robbing potential power and wear from your rebuild.

Like they say, You can lead a horse to water but you can't make it drink..
I've had a big thirst for knowleage on my rebuild and I can only hope others may benifit from my blessed rebuild and quenched appetite .

[dandywarhol]

One of the best posts I've read on here for a long time.

[cobbadiggabuddyblooo]

One last observation for all to note.. Please work out your new torque calculations if you choose to attempt to tighten the conrods inplace with a spanner not square to the nut... Cheers .. Good luck and merry Xmas... I won't go in to the physics of it all...

not just me then Cobba?


http://www.engineersedge.com/manufactur ... ench_1.htm. Another handy piece of information I learnt from Rod.