big bore crm

[bungerlowbill]

hi crm'ers , thinking of cr500 engine or is there enough meat on crankcases to graft 500 head and barrel etc any constructive micky taking greatly recieved rregards bill

[knackeredMk1]

No politically correct answer available...................

[fallenmikethebike]

EML make an even bigger single cylinder 2 stroke, stop fannying around with a 500cc
Mike

[knackeredMk1]

Maico 620 .

[Mudfacetony]

There is some 2 stroke boffin down south. ex mx rider, cant remeber who but he rode hondas. apparently he says optimum cc fot a 2 stoke cylinder is 310cc. be good if a crm cylinder could be over bored to that size

[fallenmikethebike]

Factory 400cc, that was the Paris Dakar AR ultimate evolution.
Mike

[knackeredMk1]

Stickman (of this forum. Last contact ~ a year ago) did 300cc - He had to move the PV out in the barrel to get the clearance. He also grafted a CR 250 barrel and head onto a CRM crank before this with much more success than Jeram has had to this point.

Stickman used the engine in scooter racing. I've got a dyno printout before the development was complete.............

Basically as I remember - Blue is 250 + DEP expansion chamber and exhaust. Pink is the same but with aftermarket reeds and a bigger carb. Green is early stages of 300 setup before the top end was sorted (Big mid-range!). I think the blue and pink are on seperate bikes.

[Mudfacetony]

Stickman (of this forum. Last contact ~ a year ago) did 300cc - He had to move the PV out in the barrel to get the clearance. He also grafted a CR 250 barrel and head onto a CRM crank before this with much more success than Jeram has had to this point.

Stickman used the engine in scooter racing. I've got a dyno printout before the development was complete.............

Basically as I remember - Blue is 250 + DEP expansion chamber and exhaust. Pink is the same but with aftermarket reeds and a bigger carb. Green is early stages of 300 setup before the top end was sorted (Big mid-range!). I think the blue and pink are on seperate bikes.

The mid range stacks up as my Gas Gas 300 has bucket loads of the stuff compare with the 200 KTM I used to have

[Jeram]

Stickman (of this forum. Last contact ~ a year ago) did 300cc - He had to move the PV out in the barrel to get the clearance. He also grafted a CR 250 barrel and head onto a CRM crank before this with much more success than Jeram has had to this point.

Stickman used the engine in scooter racing. I've got a dyno printout before the development was complete.............

Basically as I remember - Blue is 250 + DEP expansion chamber and exhaust. Pink is the same but with aftermarket reeds and a bigger carb. Green is early stages of 300 setup before the top end was sorted (Big mid-range!). I think the blue and pink are on seperate bikes.

For someone who claims to know what 'successful' means, you dont seem to realise that is a pretty piss weak power curve for a modified 250, let alone a 300.

I don't even need a dyno curve to tell you my CRM made more power that that throughout the entire range.

You've been bashing my bike since the start, constantly heckling my thread and posting nonsence like this in other threads

first it was "oh you will never get it finished"... you were proven wrong by the many youtube videos

then it was "you will never getting it running properly" you were proven wrong, indicated speed of 170kmh at broadford raceways back straight.

then it was "oh the engines been apart for a while now, he must have give up, fail" "unsuccessful project"
Completely incorrect, I've just had more important projects to attend to and just by coincidence the bike will be back up and running in a couple weeks and on a dyno in the new year.

Incase you realise, your buddies CR250/CRM hybrid was a complete failure, it didnt work, so Im not sure where your getting your info from. He gave up and went back to the stock cylinder. So Im not sure where you bias is coming from.

childish behavior, especially from a moderator.




To the original poster, the CR500 cylinder will not work as its a cylinder reed motor not a case reed motor, in addition it simply wont fit in any way.

There are no real big bore options that are viable in any way.
Im developing an 80mm cylinder for the CRM, but even that isnt really viable for anyone else accept me as my motor is far from a CRM now, it just the cases and gearbox that are still standard.

[helisupp]

Jeram,

If your cases are standard why will the 80mm cylinder be of no interest to us.............mine are also standard so should fit .

[Jeram]

because it will be designed for my motor (137.5mm rod, 18mm wrist pin which requires crank mods), and requires fly wheel and pickup mods to work with a programable ignition (complete bike rewire)

[Jeram]

yeah sorry, I got a little bit distracted before half way through my post as I had to go and fire up the barbie to for the end of year/Xmas BBQ at work.

yes so pretty much to get a performance cylinder with an 80mm bore to work you will need to have the following modifications done

1. crank rebuilt using a 137.5mm rod from a YZ490, 18mm gugeon pin size, requires crank web machining which I can get done for anyone who needs it (rod =$120, rebuid = $50, machining =$50 + postage)

the second mod required to do ANY big bore OR major performance mod on a CRM is the following electrical mods
-re-wire the bike as per a zeeltronic wiring diagram (doesnt take long if you can follow the directions)
-grind the additional flywheel trigger bars off the flywheel, I did mine with a hand file one nite with over a few beers and a cigar.
-swap the flywheel ignition trigger to a dual wire trigger, you can get one thats close but requires the bolt holes to be ovaled out so it fits the CRM trigger bolt spacing (not hard)

not sure what else you'd really need to do apart from installing a CR250 reedcage, get a CR250 manifold boot, a PWK38 carb and remove some material from the airbox boot coupling to accept the larger carb bellmouth... all pretty easy stuff to do.

But the most difficult part now will be getting the cylinder developed and testing and developing a pipe for it.
I will not be even considering getting any additional units untill its been tested rigorously.


But as you can see the costs add up mate,

the biggest costs are the cylinder -$600 approx
Pipe $400 (oiled steel finish or painted black)
piston - $150
ignition - $350
carb -$120 good second hand
vforce reed block - $150
rod/crank mods $220
intake rubber boot $40
ignition pickups $30

Total = $2060

As you can see by the cost its not really economically viable for most people.

I simply do it because I have a passion for performance engines and I like it when my CRM makes a fool out of big dollar CRF450 supermotos at the track.

Currently my CRM is running the 2005 CR250 cylinder bored out to 265cc with all of the above mods as well. By the way that it pulls I suspect that its making around 45-50hp with an OEM honda pipe, and could be increased to 55hp with a custom pipe. But sadly my resources are spread to thinly at the moment and I am committing everything I've got to my 421cc Cub motor to perfect it.

[bungerlowbill]

thanks you for input chaps, looks like going down the cr500 complete engine route if one comes up cheap enough anyway festive greetings regards bill

[knackeredMk1]

Bill, a thing to think about - The best part of the CRM is its engine. The frame is a little lardy and the suspension soft and saggy without some serious attention. If you want the power of a CR500 you are probably best to buy a complete CR500 and convert it to the road rather than convert a CRM frame to house a CR500 engine. You would also be able to get new plastics and graphics for a long time in the future at much less money than you would have to spend on the dwindling supply of CRM plastics.

Eight bikes on ebay at the moment. Most are almost mint though with a couple of restoration projects. CR500s do come expensive though.........

[caravanmonster]

The person I'm currently rebuilding the CRM for used to have a road registered '93 CR500. It was ridiculous for trailriding. Extremely loud even with a double skinned spanny and big silencer, vibrated like no other bike. On standard gearing it would go sideways or wheelie as soon as you came off tickover. On taller gearing, speeds not appropriate to knobblies and insufficient braking came about before you knew what was going on. Difficult to start and those weird angled kickstarts were awful. In it's defence, it was virtually indestructable and the suspension and ergos were good. Outside of old school mx, I can't see much purpose for 500 strokers in the UK.