CRM250SMR (using CR250/YZ490/KTM250SX internals)

Jeram
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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 09 Dec 2012, 12:25

Build thread is still on PBMAG forum, I asked for the other threads to be removed from other sites as there were too many trolls.

I wouldnt say too much money spent, this bike has cost me virtually nothing except for the cost of the bike.
All the mugen bits, forks, wheels, cylinder, carb, ignition have all been sold off and covered the cost of all the performance bits.


IM currently preoccupied with a much faster bike, its a golden era 500GP replica using a TZR chassis and a 421cc two stroke shop motor that puts out 90 odd hp and weighs 125kgs.
Shes all up and running and is a formidable beast to ride, as terrifyingly exilerating as an 80s GP machine

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Retro
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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Retro » 11 Dec 2012, 12:55

:BB

Jeram
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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 18 Dec 2012, 02:48

coincidentally, Im going to have all my bits back before Christmas so that I can get the CRM going again for some January and February.

However the motor wont be running for more than a few months as I am currently in talks with a cylinder casting professional who is looking into making a batch of one off cylinders for both my 2T single cylinder racebikes.
The KTMito cylinder its at its limits and cannot be pushed any further which is disappointing, while the CR cylinder I am running in the CRM is less than ideal for making good power.
Essentially it will be a scaled up Aprilia GP cylinder, around 300cc for the CRM and around 400cc for my 380 motor.

Shouldn't be nearly as expensive as one would think, as the cylinders permanent tooling (moulds etc) is mostly already done from when he made a YZ360 and some ultralight racing motors so now it just needs to be adapted to fit each of my motors which is more or less taken care of during the final machining on the CNC machine.

Will be quite fun to have a torquey 65hp, 6 speed, counterbalanced motor in the CRM,
I might be needing one of those TRX billet baskets though!

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 27 Jan 2013, 08:49

amongst preparing my TZR421 for some classic road racing events and commissioning a GP spec cylinder to be designed and manufactured for my road racer, I've managed to find time to get all the bits together to get the CRM beast going again.

Replated cylinder with a recessed exhaust bridge
new Wosner SX250 forged piston which has been machined to fit my engine
Zeeltronic powervalve controller (couldnt get my ignition to control mine)
Zeeltronic handheld programmer for altering the PV settings anywhere, anytime


Should have her all put back together in the next couple weekends.

I've got a go pro replica camera so will be able to take some video from the first trackday.

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 28 Jan 2013, 12:56

today I made the copper head gasket, made the base gaskets, modified the piston so it doesnt scrape the oil off the bore, checked the ring gap and double checked the exh and transfer port timing.

The timing is still a little high for my liking at 197/129 but that's why we have powervalves.

Just have to slap the cylinder on in the next few days, then connect up the new race ignition which has a special little feature to prevent seizures when you close the throttle at the end of the straights, as well as a map switch, gear counting and traction control.

once thats done this week Ill just have to repair the exhaust mount bracket that I damaged and install an EGT and a coolant temp guage.

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by knackeredMk1 » 28 May 2013, 17:33

Any progress :?: .

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 27 Dec 2013, 04:23

nope...

I'm in a sticky situation at the momment.

Wiseco stopped making the pistons I was using, so I ordered a Wossner piston but it was faulty, so I ordered another and it was faulty too. So I've concluded that all Wossner 1996-99 265cc KTM250SX pistons are faulty so I'm stuck without a piston for the bike :(.
The problem with the piston is that the piston ring is free to move (rotate) when then piston is in the bore which can (will) cause catastrophic damage when the ring catches the exhaust port window.


So I'm at the point in time when I have make a decision either to have a custom piston made or to go back to using the AR cylinder but try to extract as much power as possible. I think a genuine 35-38hp at the rear wheel will be possible with the standard cylinder without too much effort. It isn't much but it will have much more low end grunt than the CR cylinder.

Ill be making the decision on what to do in the next week.





But in other news, I got the KTMito 380 fired up finally after some solid hours were put into finishing the pipe and the ignition.

http://www.youtube.com/watch?v=eNg1tzsR-6M

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by mekros » 02 Jan 2014, 20:29

Do mitaka make a piston you could use?

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 03 Jan 2014, 03:28

mekros wrote:Do mitaka make a piston you could use?
Not that I know of.

If you can find one, let me know.

I just need a KTM250 - 1999 piston in a 68.50 size that isn't a wosner.

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by mekros » 04 Jan 2014, 06:42

Vertex claims they have the piston you need, I don't know if it is a big bore or standard piston though.

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by Jeram » 07 Jan 2014, 03:07

mekros wrote:Vertex claims they have the piston you need, I don't know if it is a big bore or standard piston though.
everyone has the piston, but nobody has it in 2mm oversize ;)

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Re: CRM250SMR (using CR250/YZ490/KTM250SX internals)

Post by mekros » 07 Jan 2014, 17:35

2mm oversize is a fair whack though!


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