Project "casualty"

[CRM]

ask me in a week - its there next week
its going in for - custom gearbox to suit supermoto, squish set, jet and tune and dyno setup.
reliability and grunt is the end game over outright top end bhp.
either way i predict 10 more bhp over the CRM and 15 kilos less weight and a likely to be the only one gracing a trackday.

[Occams Razor]

That's going to be "lively"

[yazza5454]

ask me in a week - its there next week
its going in for - custom gearbox to suit supermoto, squish set, jet and tune and dyno setup.
reliability and grunt is the end game over outright top end bhp.
either way i predict 10 more bhp over the CRM and 15 kilos less weight and a likely to be the only one gracing a trackday.

Cool, you're going to the right man

[CRM]

facinating guy
we discussed ratio's and gearing scenario's
apparently my stock bike with a 14/38 gearing will manage 94 mph
however with such a huge gap between gears it will be constantly out of the powerband and unless running down hill and weighing 6 stone then it's an impossible speed

So with his gearbox i can manage 92 mph, but be always in the power and even at my 16 stone bulk seeing 90+ is likely.

I could have opted for a 6 speed box, but at £2000 i thought it was a tad extravagant even on this project lol.

I am looking forward to my dyno before and after's
60bhp is expected and normal for a healthy and well setup CR250, that's quite a bit more than my old CRM so it could be quite an animal this thing lol

[yazza5454]

facinating guy
we discussed ratio's and gearing scenario's
apparently my stock bike with a 14/38 gearing will manage 94 mph
however with such a huge gap between gears it will be constantly out of the powerband and unless running down hill and weighing 6 stone then it's an impossible speed

So with his gearbox i can manage 92 mph, but be always in the power and even at my 16 stone bulk seeing 90+ is likely.

I could have opted for a 6 speed box, but at £2000 i thought it was a tad extravagant even on this project lol.

I am looking forward to my dyno before and after's
60bhp is expected and normal for a healthy and well setup CR250, that's quite a bit more than my old CRM so it could be quite an animal this thing lol

Nice one, yep he's very knowledgeable

Did you see any of the kart engines there? There's a 250 single he developed himself which is pretty cool, got his own cylinders cast, billet cases etc. the 250 twins are smart too, gotta love a 100hp 250 stroker

I'm sure your bike will go great

[CRM]

i did and i was asking about it
there was nothing original CR250 left on it, a proper trigger's broom.
he knows exactly what i will be using it for and seemed confident i should stick with genuine OE pistons and rebuild the top end twice a year at my current use rate and bottom end every 2 years.
parts are cheap, even i can do the piston, but to be honest i cant see why he wouldnt get the work and support it.

[CRM]

#Update

So Ian at Viper has been in touch with initial findings and as a summary is like this
first run it made a very poor 43bhp and is way way too rich though out the range.
also worth noting at 9500 rpm it advances itself to death - thus firing way before compression which obviously is not ideal and going to put negative forces on the motor, generate heat and make shit power.

So next step is a custom ignition (jd racing) to try and sort the advance at the end, if it doesnt then there is a chance the DEP pipe could be causing some issues.
So i can see a custom igntion being required (fuck it - in for a penny, in for a pound and if it needs it it needs it)
jetting and squish is clearly to fuck too. so it appears it's all win win from this point on
but he is confident high 50's will be very easily achievable if not more.

I can't wait to try and tame this thing lol

[CRM]

Well a month on much has changed.
The bike was completed and had quite a bit of time being setup by Ian @ Viper racing who specializes in carts that use the CR250
It was evident all was not well on the first few dyno runs and the power was low 40's and with a horrible tail at the end of the rev range that went not only seriously lean, but the ignition curve advanced early on the original ECU in an effort to curb over revving.
clearly this has quite a negative effect on the engine by firing the ignition before TDC thus putting negative forces on the crank and engine.
This was not the only issue. the garage i bought it from had fitted a new original piston as part of the deal - sadly the muppets fitted a 02 - 04 piston that is flat domed and not the correct domed 05 - 07 item. as such i was down a bit on compression and CC so that needed sorting.

So now with a new piston, custom ECU and maps and PV set correctly the beast was making high 40's bhp and a nice healthy curve.
running the 14 / 38 gearing with 17" wheels it was topping out at an indicated 106 mph @ 10k rpm, so with some minor limiting and jetted to suit it was ready for it's first outing.

So on the 20th i rocked up to RAF Valley ready to enjoy this and give it it's first maiden run.
The first session was very nervous, brand new tyres, new bike, new brakes and running the new piston in.
Very quickly i managed to pop a fork seal on the brakes that then dumped all its oil over the front disk making stopping quite interesting. however i carried on and really enjoyed the bike and even managed to pass a few sportsbikes in the corners.
the grunt coming out of corners was impressive i have to say, faster than the CRM and way way lighter to ride with much firmer suspension.
Was i any quicker on this than the CRM ? possibly not no, tyres, brakes engine i suspect had i have been on the CRM i would have been quicker.





Come the second session, a quick top up of fuel (Christ it likes a drink of the old 32:1 mixture this thing) and out i go
a warm up lap then i was off like a greyhound out of a trap and the bike was flying. quickly started to catch up the back end of the group and the bike was effortless to scythe around big cumbersome heavy fast bikes in the slower corners but come to the long straight it was on the limited and topped out doing over a ton at less than third of the way which was frustrating.
in my mechanically sympathetic mind i thought it best to back off a bit on the long straight by running at part throttle - big mistake.

now when i say big mistake i mean - like really big, i would have been better simply shutting off the throttle or keeping it pinned and not going half way house lol
as such the inevitable happened - i seized it. I felt it start to slow so quickly whipped the clutch in where it stopped dead. i coast to a slower pace and try to free it with a bump, much to my surprise it starts and runs fine so i nurse it back to the pits where i sit and sulk for a bit.

As such it was loaded back in the van and i borrowed Paul Tye's (tye noodles) well sorted NC30 for a session before an early bath.

[CRM]

So the next day i had decided i wasnt going to bother returning to Valley but after waking at 6am i thought better of it and leapt out of bed to quickly load the van with a working bike and make the most of the day that was paid for.

So after a quick mental descision to take the trusty RVF and after a quick argument with myself i ended up loading the RG500 gamma up for a days thrashing because of the following reasons - it had more petrol in it !!
And boy i was glad i did, i had more fun wobbling around nervously on skinny tyres and weak brakes having epic fun - sorry but the RVF as good as it is, it fails to deliver the same smile and cheezy grin at the end of each session.

[CRM]

So back to the CR250
Well after a strip of the top end by Ian, he confirmed a pretty unlucky seziure.
by unlucky he said another hour on that piston it probably wouldnt have seized and it was only because it was still a little tight and the gasses couldnt escape quick enough at high RPM coupled with my part throttle actions.
So with no damage done a new piston will be fitted, up one size on the main to cater for reliability over outright bhp, a new set of genuine honda forks seals and she will be good to go on the next track day. . . . . .

However . . . . .

My love for the CR has grown and as such i am finding myself not happy with the odd mark here, the odd scratch there and it may well be the last of the classic 2 stroke CR's being an 07, but it's still a motocross bike that's been "used"
So after a couple of inquiries idle curiosity took hold and i wondered if there were any new old stock CR's sat in crates somewhere like a fairy tale that i could buy and have a brand new bike.

Well funnily enough i found the next best thing - i managed to secure a 07 CR250 that has been used once.
yes once, and by once i mean - filled with fuel, started and run up a private dirt track when new then parked for 2 years after cleaning before being bought by someone else as an investment who then cleaned it to death and then parked it in a spare bedroom in parts for the next few years.

So it would appear i have now purchased this other bike and it really is as new, original tyres are still un worn, one small mark on the swing arm, seat cover replaced with a pattern item after something fell on the seat and put a hole in the cover, but more importantly the bike, engine, frame and all parts are new and un faded or corroded or even aged. - this is the bike for me.
It is easy to keep a new bike looking new, but much harder to get an old bike looking back like new.

So the plan is as follows
Switch all the nice SM parts over to this new bike
put the original bike back to exactly the same spec as i bought it (with new piston, jetted and setup correctly and new fork seals) and sell it on next year as a road registered bike - i can't lose money on this and it will sell easily.
Road register the new bike - this could be a painful process but worth it.
use the new bike for short twisty circuits next year and use the freshly rebuilt CRM for anything with a longer straight involved.