Performance - 1980 PE 400 vs RM 400

[Barra]

Im finding my PE 400 to be lacking a bit in low / mid range grunt. I reckon it should be better. No probs with motor which is in A1 nick, but has been ported a little which i'm suspecting doesn't help. Top end performance is great.

Can anyone tell me how a standard PE stacks up against a standard RM is this department? Is the difference huge?  Is it worth considering swapping to RM specs / barrel to get more grunt? (I like to steer with the back wheel!) Or are there better options to get more low/mid range 'lift'?

[frostype400]

Maybe it is your ignition stock they pull great low to mid matter of a fact they hit a wall up top stock and you short shift rather than revving its guts out.

I have a different ignition unit in one of mine but I am yet to try it though. Standard with Cdi isn't that great but depending on a couple things pipe port height ignition will have an affect.

The rm400 is more a top end machine than the pe from what I have read so swapping to rm specs probably won't get what you want.

[oldfart]

Frosty .... your spot on. You need to short shift as all the power is down low, and the tend to vibrate like hell with revs ( pins and needles in fingers big time ).
Check to see if timing is right ... factory marks .... get jets right ..... I'm presently running  290 main with a 50 pilot... using a KX 500 piston 
Remember reading an article that rated the Pe with more Hp over the Rm.

[TT5 Matt]

as soon as you raise the exhaust port your bottom end grunt goes out the window, my ts185a did and no good for puttering about the paddock looking for 3 corner jack plants but its great for dirt tracking. maybe Looza has a pipe and combustion chamber reshape that will give you back some of that lost bottom end grunt but a 400 should have plenty in any case compared to little motors like 125/175's

[euro bikes]

They are different motors PE has a shorter stroke .

[Lozza]

Im finding my PE 400 to be lacking a bit in low / mid range grunt. I reckon it should be better. No probs with motor which is in A1 nick, but has been ported a little which i'm suspecting doesn't help. Top end performance is great.

Can anyone tell me how a standard PE stacks up against a standard RM is this department? Is the difference huge?  Is it worth considering swapping to RM specs / barrel to get more grunt? (I like to steer with the back wheel!) Or are there better options to get more low/mid range 'lift'?

At first was hard to believe the PE had the big bore short stroke compared to the RM.  Depends on what was modified in the cylinder if that's what lost the mid range. Comp always helps. 

[Barra]

They are different motors PE has a shorter stroke .

OK thanks. Well that answers one question I guess!

I suppose I am trying to establish a base to work from - how does the PE compare to RM in low to mid range? Without having another to compare to, I need to know how much power a PE should have.  Does anyone have one of each who can say for sure how they compare? 

I remember having my first ride on the PE (many moons ago) and thinking "this things got some grunt!" - and i was coming off 84 KATO 500's, the ultimate tractor motor!
Then after 4 years (and the port job) I had my next ride - bit hard to compare the feelings 4 years apart! So i'm not sure if i lost mid range power in the process??

I guess i can sum the bikes performance up by saying that when i exit an off camber grass track corner, i either have to dial on the throttle and wait for the power to kick in (frustrating) or clutch it like a 250 and risk getting out of shape. I want to steer with throttle but cant! I would have thought this motor should be capable of that.

As far as the motor goes -  it is in new condition, i've explored all jetting configurations (runs clean) and the timing is already a touch advanced (so in theory should have more grunt?) Going richer on pilot and/or needle only worsens things.

I'm thinking its a port timing / pipe thing?

[80-85 husky]

put an rm 500 motor in it....

[TT5 Matt]

your pe will have a wide ratio box like my 185 has as useless for track work, lucky for me a tm/rm125 box slots straight in but couldn't say weather an rm400 close ratio  box will go into your pe400.maybe a secession on alpha sports web site will tell you if in/output shafts/selector drums etc are the same for a mix n match of gear sets

[mainline]

your pe will have a wide ratio box like my 185 has as useless for track work, lucky for me a tm/rm125 box slots straight in but couldn't say weather an rm400 close ratio  box will go into your pe400.maybe a secession on alpha sports web site will tell you if in/output shafts/selector drums etc are the same for a mix n match of gear sets

I was under the impression the PE400 engine was based on the RM250 motor, so that gearbox would probably be a better chance of fitting.

The VMX mag review on the bike basically said the same as Michael. All grunt and to be shortshifted. They said that it was more than a match for the RM400 in terms of power except for maybe a pro rider who could ride with the throttle wide open.

[g465b]

these figures are from cycle guide magazine back then,  rm400- 417cc   80mm x 83mm / pe400  397cc    85mm x  70mm
     
     dyno  hp@rpm      3000  3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
                 RM400       8.5     13     15.5   18.3 22.3  25.4  27.1  28.7  29.7  28.1  25.8
                 PE400        8.6    12.5   13.3  15.9  19.9  26.8  28.1  28.5  30.9  30     30.4
   
               torque  ft/lbs           
                 RM400       14.9  19.5    20.4  21.4 23.4  24.3  23.7   23.2  22.3 19.7  16.9
                 PE400        15.1  18.8   17.5   18.6 20.9  25.6  24.6   23    23.2  23.2  20

      rm  14/49 t   104kg      pe   15/46    113kg

[frostype400]

You sure your reeds are ok what are you using standard metal or Boyeson or something else.

My 400's I can fly though corners with ease and look at the back tyre while powering through the corner that is on hard dirt roads get a lot of wheelspin all the time on grass or dirt any other surface can pull a wheelie in 1st 2nd and 3rd well can still lift the front in 4th and 5th with a bit of rider effort.

My sense is if you think you are down on power you are.

[bigk]

PE400 engine is much nicer than a peaky RM400. RM400's are fast for sure but very tiring especially if you big bore them with a Maico piston. That's my experience anyway.
K

[Barra]

these figures are from cycle guide magazine back then,  rm400- 417cc   80mm x 83mm / pe400  397cc    85mm x  70mm
     
     dyno  hp@rpm      3000  3500 4000 4500 5000 5500 6000 6500 7000 7500 8000
                 RM400       8.5     13     15.5   18.3 22.3  25.4  27.1  28.7  29.7  28.1  25.8
                 PE400        8.6    12.5   13.3  15.9  19.9  26.8  28.1  28.5  30.9  30     30.4
   
               torque  ft/lbs           
                 RM400       14.9  19.5    20.4  21.4 23.4  24.3  23.7   23.2  22.3 19.7  16.9
                 PE400        15.1  18.8   17.5   18.6 20.9  25.6  24.6   23    23.2  23.2  20

      rm  14/49 t   104kg      pe   15/46    113kg

Thanks g465b those dyno figures reflect exactly what i feel the motor is lacking. Surprisingly its good up top but i dont like like revving a big vibrator that hard.
Frosty, brand new Boyeson reeds. 

I'm now guessing a stock PE motor would be better than mine? If for example, the exhaust port had been raised 2mm, what would be the best route to get things back on track? Weld up the ports? Drop barrel and machine head?   

[frostype400]

You might be better getting a spare cylinder rather than reverse modifying yours so that you can start stock and then you will know you'd hate to change your cylinder to find you preferred it how it was.