pe175 performance questions

[80-85 husky]

the pe175 is a rip tearer once you get them right. there is a bit to do. 1. alloy muffler, 2 timing set to specs. 3. rejet to suit.
from the factory they were restricted and once they were removed, you had to reset timing jetting to std as they were altered to cope with the restrictors.

obviously now it would pay to strip motor and redo seals, and while its apart, get the transfer ports matched to the barrel and get the barrel ports tidied up as in open up and clean all dags, match them to the base gasket etc dont remove any metal from the barrel, leave the port timing std. clean up the intake port and knife edge any dividers etc.

check the exhaust pipe, they may be double walled so a real good clean would be in order. a new carb would be best unless its in real good low hours condition. boyson reeds top off the package.

you should finish with a real snappy quick revving engine, not a great bottom end engine but something that jumps into the band at the snap of the throttle and pulls hard across the range. would be fun to ride, a real zinger!

if you want a bike that crawls up hills in 3rd gear at 1000 rpm, the pe isn't for you! KDX 250 is the standout tractor of the 80's aircooled engines

[Lozza]

..................... knife edge any dividers etc.

Under no circumstances should that ever be done on any engine. I forgot about the pipe restrictors they are worth removing.


Increasing the compression ratio will help bottom end.

[80-85 husky]

please explain? Knife edging?? whats the deal?

[Prospector]

I have a 83 PE 175, not so good down low but when you keep the revs up its quite good,  very nimble in the tight stuff but it's a single shock. I have a 80 PE 250, it pulls real well down low,  my choice of the 2 for power delivery,  it would have been great if the 250 carried  on for another year or 2 and they built a single shock floater.

Cheers Pete

[rocketfrog]

Yep the knife edging is a sure sign of a back yarder with a die grinder from supercheap who is all of a sudden better than Frank Pons because he heard from a mate this is the go........

If I pull a barrel that the back yarder has knife edged, I usually resign myself to sourcing a replacement barrel beacause if someone has gone that far it is not too much of a stretch to believe that other "performance Mods" have been carried out. I pulled down an engine not long ago that had the classic houso porting plus a turbo crank - slotted with a grinder (but get this-it was done in situ!!).

Moral of the story is do your research, get the word from an expert or pay an expert to do the work. (discuss what you want from the engine)

Generally the factory has researched and developed the design to very acceptable standard, manufacturing flaws such as dags in the casting and port mismatch is usually the only work required to get good reliable power from a Jap performance engine.

Blue printing the stock engine will be best place to start in most cases, that way you will know how well the engine will perform as the manufacturer intended. This is a good place to start - baseline the bike - suck and see.

Carefull attention to detail makes a noticeable difference and is indeed all that most privateers delve into ie; blueprinting, carefull attention to build up and test and tune until the bike is dialled in to suit the rider.

If there is any short fall, performance parts are added to fix the short comings - emulators, aftermarket silencer/exhaust, carb, bars, pegs, springs etc.

[Lozza]

please explain? Knife edging?? whats the deal?

It has to do with sonic and sub sonic air flow. Like aircraft wings sub sonic aircraft have rounded leading edges on the wings and sharp trailing edges. Super sonic aircraft have sharp leading edges on the wings. There is no super sonic flow in an engine , therefore it is a pointless exercise.........not that I've ever done it 

Yep the knife edging is a sure sign of a back yarder with a die grinder from supercheap who is all of a sudden better than Frank Pons because he heard from a mate this is the go........

If I pull a barrel that the back yarder has knife edged, I usually resign myself to sourcing a replacement barrel beacause if someone has gone that far it is not too much of a stretch to believe that other "performance Mods" have been carried out. I pulled down an engine not long ago that had the classic houso porting plus a turbo crank - slotted with a grinder (but get this-it was done in situ!!).

Ha ha nearly spat my coffee everywhere. I'm even thinking now that removing dags and gasket matching is a WOFTAM. The next biggest sin is the step at the exhaust flange/cylinder, which is put there deliberately. Imagine what a Supercrap die grinder could do to this 54hp $5000 cylinder 

[shelpi]

LOL

[80-85 husky]

that cylinder should be in the Guggenheim

for a little bit of $$ at a muddaboik man, the tidying up of the transfers and cleaning up of the edges is worth the $$.

its basically a blueprinting, not a "port job"

I have not suggested in any way shape or form that the port timing be altered. I have had considerable success doing this to several bikes ive owned.

this is just making the engine as good as it can be to compliment new seals bearings etc etc.

it seems to me to be a waste of time to split cases and spend a $k + refreshing the bottom end and not blueprint the ports especially if there is considerable gasket overlap and thick daggy bridges....

[TT5 Matt]

old small files round/flat/square profiles bent to shape are good for tidying up the ports and for a few hrs work of blending youll get good gains for little money and a freer reving motor

[Lozza]

if you think that all that will make a difference it will regardless of what a dyno or a stopwatch will tell you. In a kart catagory I was tuning engine in there were specific rules against cutting your own base gaskets and having a large over lap, I always wondered why until we tried it. The overlap actually made the duct more efficient(engine could be leaned off and was 0.2-3 sec faster) as it was to big and the wrong shape. With 2 strokes nothing is as what it seems.

[TT5 Matt]

so your saying abit of base gasket protroding in the transfer ports causing an restriction is a good thing??

[80-85 husky]

supersonic air in them cart engines

[pokey]

if you know what your doing with ports and the effect a change has on the rest of the engine then it can be a good thing but if you dont then best go to the fridge and grab another beer and put the tv on and watch the cricket. i think we all know that if you pick up on one area it has to come from somewhere else.

All Ive ever done to a top end is basic clean up and  match the ports and the piston skirt  to the factory specifications, smooth exhaust port and CC. yeah Blueprint.
 End result is stronger smoother engine performance that comes close to the factory sales blurb and still have reliability and a tractable engine.

i kind of like the notion of sand cast intake having a larger effect of emulsifying the fuel vapour more than a smooth intake that would only have drag and emulsifying effect on the peripheral zones. Im probably wrong  but for no effort it works good and if it was good to have a smooth intakewhy didnt factories just do a straight clean machined intake and why did suzuki create the TSCC (twin swirl combustion chamber) on its 4t GSx750?

i have 'corked" a counterweight and i think it went better but i was 17 at the time so maybe the fumes or my mates sister  made it feel better.

[twinrock]

Wow this has certainly turned into quite the discussion, i am no expert and am still learning the mystery of the 2t engine even though i have been riding and building them for 20yrs now..mostly road yamaha twins and Suzuki..but loving dirt riding now but know very lil about the bikes..yes knife edging has been frowned upon for sone time now over the rounded transfer bridges..i agree that manufacturers know what they are doing..BUT.. still have to make compromises due to noise, emissions and reliability constraints. They also suffer the flaws the mass production brings So in my experiences the general tidy up of castings and transfer flowing does make a notable difference..its seems to make more if whats already there..not change the characteristics of the motor the way making changes to ports does..so back to the suzuki pe175 it would seem that the performance characteristics i have questioned are the general census..no clean up or knife edging is going to change that ..only port timimg and an exhaust to match...thanks guys i have enjoyed the lesson

[skypig]

The next biggest sin is the step at the exhaust flange/cylinder, which is put there deliberately.

Really?

I blended this on an RM125 in 1981 as a bit of an afterthought.
It made such a difference I was kicking myself for not doing it earlier.