RM/PE 250

[adam.m]

Im looking at buying a 1978 PE 250 and wondering how suitable it would be for VMX.
Is the PE 250 pretty much the same as an RM250 ?
Is there much available in after market parts ?

[boyd40]

The RM 250 has substantially different porting. It is much peakier, but makes a lot more power.
I have wanted to try modifying a PE cylinder to improve the PE, but not lose the nicer power band.
If you go this route, make changes to the exhaust port height in small increments (0.5mm).
wayne

[80-85 husky]

Good power can be had from the PE by simply using a good alloy muffler, set timing correctly, increase main jet size to suit muffler if required.

if you strip the top end, match all the ports to the base gasket carefully and clean out any dags  and knife edge any bridges.

if you split the cases, match each transfer carefully to the barrel / base gasket and this will assist the motor to run as best as possible before actually altering the ports if your chasing more go.

as boyd 40 said if you raise the exhaust port, you will lift the revs that the power will hit at and it will hit harder.

a larger carby may also give more top end but you could loose midrange.

The PE will give a strong powerband, not as hard as the RM but much easier to ride IMHO

you need to decide if your building a competitive mount or a drag it out and ride it for fun bike.

once the timing jetting and muffler are right, money spent on forks and quality shox will see better lap times

[oldfart]

Davey Crocket .... wobbles around on a Pe 250 C on practice days and recons the gear ratio spacing's are too tall ......Joan it's time for you to chime in 

[Lozza]

Im looking at buying a 1978 PE 250 and wondering how suitable it would be for VMX.
Is the PE 250 pretty much the same as an RM250 ?
Is there much available in after market parts ?

Pipe has the biggest influence on the output curve, and as Stewart said that has to match the gearbox. You don't need to raise the exhaust port and knife edging dividers is a useless exercise. As always the bigest gain is in suspension.

[OverTheHill]

yes, gear ratios could be annoying if the power's improved up top at the expense of some torque lower down which seems to make enduro spaced gears stand out even more. Even on my 490k which i accidentally fitted an it465 5 speed box [bought off ebay as yz465 ahhh] the spacing is annoying in soft or muddy going bugger it. Getting back to the PE, squeeze some more compression out of it & run it on race gas, make sure the pipe & muffler are clean clean clean, think PE's have a restriction somewhere near the back of the tail cone, or was that 400's [someone will know]--or put a 'good' aftermarket pipe on, [preferable]. My thoughts for the day.

[Montynut]

Seriously I would suggest the best progress for a PE250 would be to de-restrict the pipe, silencer and airbox and then rejet to suite take off anything not required. Freshen up the top end and accurately set the timing and then work on the suspension & brakes.

You will enjoy the racing much more on a standard engine PE with great suspension than a standard bike with a modified engine. Fit PD valves & correctly weighted new springs in the forks along with properly set up modern shocks for the rear. Replace swingarm and steering head bearings to let the new suspension do its work.

Once you have the bike handling and working well I would think you will find it is more than competative in club VMX racing. Certainly there are several members of Heaven that have consistently been in the top 10 of 250 EVO with PEs and ITs. Presently the EVO 250 class is dominated by a Husky WR250 '81.

As always it is more a good rider on a well set up bike than a highly modified engine than wins in MX

[shelpi]

put a RM donk it (with Rm PEI) change carby to RM jetting remove exhaust restriter a the approx 8-9 tenth mark at the rear of pipe, use Pe front wheel has the larger brake drum, put the full nine inchs up front and dam good shocks on the rear and now ya have real fine steed

[Davey Crocket]

I race a PE250B up here in QLD, 1st gear is very low, 2nd and 3rd are perfect but there is a big jump to 4th, like your going to 5th and the same for when you go to 5th....it's a great bike to ride, I put Works Performance shocks on the rear, RM125B forks on the front and a GMC RM250 A/B/C pipe on it....oh, and a rebore(it was on std when I got it....put a Woosner piston in it). The pipe makes a huge difference and the jetting went to like a 290 main, I love the bike, you loose a little in a straight line drag if it's long enough but it's a great feeling when you beat the motocrossers. The B has a huge front brake that stops better than the mx'ers. Theres heeps of parts available and there very reliable, they come out of 2nd/3rd gear corners really well. You can put the RM ratio's in them. Leave the headlight on then you always have a good excuse for not winning ...I have won a few races on it .  go for it.

[TM BILL]

Agree about the GMC pipe put one on an RM 250B and more and better power everywhere 

[shelpi]

oh yer put a RM tank an seat on, even if its off a 125, cos I had a problem with the PE tank and the family jewels :'(  at the CB Nats when my seat and tank didnt arrive in time, addmitadley I am a shorts ass