Tuning a 82' DT250 engine

[MrGix]

Would a DT400 barrel piston crank and rod fit the 250 crank cases???

I know all the usuall tuning mods but the bigger the bore the better the starting place!

I've solved one huge problem, i've reduced the weight by 50kgs at least by having a super light TZR 125 chassis, and some more to loose with spoked 17" alloy rims onway.

I need to get Gibson to make a exhaust for it as its now a road going bike,i want one that fits properly!!!

I noticed the expansion on a trial/dirt bike of the DT's era/type has a longer front pipe before the expansion than a road bike.... does that affect the rev range of torque? ie make it happen lower down compared to road bikes??? as my YPVS exhausts started the widening to the expantion almost as soon as they left the barrel.

Any idea's??? Share them here please.

Nick.

[JUST ME!]

Hi, I take it you are constructing some sort of hybrid road racer. You probably will get the 400 top end to work, if you decide to go ahead with it, get the whole show rebalanced. I don't know if you intend on road registering it, but i think a water cooled YZ250 engine would be a better thing. More power straight up with no rooting about and very reliable.Even with the radiator this engine would be a fair bit lighter. FOOD FOR THOUGHT!

[MrGix]

Hi, I take it you are constructing some sort of hybrid road racer. You probably will get the 400 top end to work, if you decide to go ahead with it, get the whole show rebalanced. I don't know if you intend on road registering it, but i think a water cooled YZ250 engine would be a better thing. More power straight up with no rooting about and very reliable.Even with the radiator this engine would be a fair bit lighter. FOOD FOR THOUGHT!

Stuff of dreams mate, its a budget racer at best.

I thought about the YZ route but money was a object there, big pennies buys a YZ lump and the cdi ect???? whooo up.

The TZR chassis came free the DT engine cost me £67.09 on EBAY... The only real expence will be the pukka 05 TZ250 bodywork and the spoked alloy rims.

Cheap hacks rock, This one may take time but it'll be one of the cheapest fun bikes around.

Be tight go far.

[JUST ME!]

Stuff of dreams mate, its a budget racer at best.

I thought about the YZ route but money was a object there, big pennies buys a YZ lump and the cdi ect???? whooo up.

The TZR chassis came free the DT engine cost me £67.09 on EBAY... The only real expence will be the pukka 05 TZ250 bodywork and the spoked alloy rims.

Cheap hacks rock, This one may take time but it'll be one of the cheapest fun bikes around.

Be tight go far.

Geday mate. All of the above is fair enough but anyway you look at it, short of leaving the DT engine how it is, it is still going to cost you money. The 250 DTs never revved well and an unbalanced 400 modded version will be worse! The 82 model aircooled IT 465 engines were a great motor, but i don't know if they were in the UK and these only had a 5 speed box.The 250s out of the 82 onwards were also good and had a 6 speeder. Lengthening the consistent diameter pipe at the start of the exhaust increase the midrange at the expense of the top end. Some of the old timers use to speak about reducing the volume of the crankcases by lacquering the inside surfaces. You would have to contact someone more knowledgable on this technique to advise on the power gains. All good fun, just be careful that the money you spend on a pig of a donk doesn't end up equating to the cost of a good one. In my opinion even the early air cooled YZ 125 engines are better than the DT engines. If your a light weight they will scoot along quite well.

HAVE A BLAST!