OzVMX Forum
Marque Remarks => Suzuki => Topic started by: Barra on May 21, 2014, 03:45:39 pm
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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'?
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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.
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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.
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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
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They are different motors PE has a shorter stroke .
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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.
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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?
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put an rm 500 motor in it.... :D
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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
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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.
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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
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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.
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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
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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?
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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.
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If you haven't already, set up the squish and compression ratio before you do anything else. Quick, easy and cheap - the best bang for your buck in any two stroke.
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You mentioned that you advanced the ignition. In my experience, that won't help with torque, which I was you are chasing for bottom to mid grunt. Try retarding the ignition timing a couple degrees. Gary Jones put me onto this with sorting out the light switch power delivery on my old Elsinore. It made a whole world of difference and the bike actually had some bottom end grunt! And so did fattening up the pilot jet....
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a rich needle will also give a hit onto the main jet a bit harder than if its spot on.
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As Lozza said Compression is a start so fixing the combustion chamber is first,
Ignition / Flywheel weight is second,
Expansion Chamber mods third.
PE 400s suffered from flywheel magnets separating from their epoxies
For VMX I would replace the entire ignition system with a more modern system say early 2000s 250 from a wreckers,
I can't remember exacts but it was cutting both header and mid body and the result was more mid range hit
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Thanks all.
Carbie is next to new. I had the jetting 'fat' and gradually backed off on the pilot and needle position to find the right combo and running clean (or maybe still just a tad rich)
I've been wondering about the timing. Backing it off will be worth trying by the looks.
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As Lozza said Compression is a start so fixing the combustion chamber is first,
Ignition / Flywheel weight is second,
Expansion Chamber mods third.
PE 400s suffered from flywheel magnets separating from their epoxies
For VMX I would replace the entire ignition system with a more modern system say early 2000s 250 from a wreckers,
I can't remember exacts but it was cutting both header and mid body and the result was more mid range hit
Thanks Son. On ignition, what if the original was in perfect nick? Would a modern replacement still make a difference?
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Carburation is last,
Combustion chamber needs help, the flywheel is fine for Vinduro and most normal people but you appear to want more so a more modern ignition curve will give you that,
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After spending the last 8 years installing and dyno tuning programmable ignitions I have yet to see more than 0.2hp difference in any engine by changing the ignition advance(by as much as +/- 7deg) , off the pipe. All adding advance will do is help the engine get on the pipe faster.
With that said it's of no use moving the stator around unless you know how much advance/retard your ignition currently has. You will more than likely find that the standard settings (measured with a dial gauge and strobed against the flywheel) provides the best "all round" performance and usualy 1 width of the stator mark either side of the reference mark is for fast and slow tracks. Modern DC/DC ignitions have far more voltage delivered to the plug, regardless of rpm, more accurate timing and smaller and more compact flywheels/stators. Along with 3D mapping etc etc
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After spending the last 8 years installing and dyno tuning programmable ignitions I have yet to see more than 0.2hp difference in any engine by changing the ignition advance(by as much as +/- 7deg) , off the pipe. All adding advance will do is help the engine get on the pipe faster.
With that said it's of no use moving the stator around unless you know how much advance/retard your ignition currently has. You will more than likely find that the standard settings (measured with a dial gauge and strobed against the flywheel) provides the best "all round" performance and usualy 1 width of the stator mark either side of the reference mark is for fast and slow tracks. Modern DC/DC ignitions have far more voltage delivered to the plug, regardless of rpm, more accurate timing and smaller and more compact flywheels/stators. Along with 3D mapping etc etc
I agree. Modern ignitions with much smaller rotors and better pick ups/stators are so much easier to live with. And they give a much fatter spark from near zero to whoa.
Changing ignition timing won't get more power, but you can change the way the power comes on, both in 2st and 4st engines. As you say, advance makes everything happen quicker. Myself, I like having a little retard on my 2st bikes as it helps to give a bit of bottom to mid range power that doesn't come on in one big explosive burst. It actually helps to make the motor more tractable. After years of being told to advance the ignition, Gary Jones put me in the right direction.....
Personally, I'd try going bigger on the pilot jet. Put a big enough jet in there to make the bike "burble" at 1/8th throttle (just opening), then remove it and go 2 sizes smaller. This should put you in the ball park. GJ also put me onto this.
And yes, expansion chambers make a huge difference to how a 2st engine behaves. My memory of my old PE400 was that of a very tractable motor with heaps of low to mid torque. It had the stock chamber but I put an alloy silencer on it for no other reason than to save the original from battle scars.
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As a rule of thumb all PE's, IT's and KDX's have more low end than their MX brothers.
You can talk about ignitions, combustion chambers, jetting and expansion chambers all you want but if the barrel has been wildly ported you will be forever chasing your tail trying to get the low end grunt back.
Step one; take the head off and measure down to the top of the exhaust port.
Then try to find someone with a known stock barrel to give you the stock measurement.
Raising the exhaust port is the first thing a lot of guys try when they get their first die grinder or dremmel, they don't always do it wisely.
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Raising the exhaust port is the first thing a lot of guys try when they get their first die grinder or dremmel, they NEVER do it wisely.
Fixed for you :)