Making a 2 smoke run backwards.

[Boostinjdm]

Another thread kinda got me thinking so let's see what everybody else thinks.

What are the things that stand in the way of making a 2 smoke run backwards?
I am talking about one that doesn't currently do so.  I have read in many places that a 2 smoke will run backwards if set up properly.

This is what I have come up with.

Oil pump not pumping oil.  You can get around this by mixing fuel.
Water pump pumping in wrong direction.  I don't think this will be a problem, but enlighten me.
CDI and retarded ignition in reverse.  I think I have a simple solution.
Starter motor not turning the right direction.  Maybe mount a second starter facing opposite way.
CVT not functioning.   May be a non issue cuz you wouldn't expect to go balls out backwards, but I don't know what would happen spinning in reverse.  I see some drivens with ramps in both directions.

[plkracer]

If they are rotary valve, they may not have the right timing I would believe.

[SPEC]

Boost I think you got most of them on  the head
I dunno and don't care what they do to make the new sleds run backwards...I could talk to Bruce tomarrow...my service guy...they carry ski-don'ts...
Harley used to make a golf cart that ran backwards in a golf cart...that was their reverse...that was a 4 stroke...but then again Harley used to retard or advance they're ignition to make threir bikes go faster or slower

[Admin]

drive clutch isnt gonna care what way it runs, it will still throw the weights..

[Boostinjdm]

If they are rotary valve, they may not have the right timing I would believe.

I read that somewhere and had to do a little research cuz I have never actually seen a rotary valve engine apart.  I do believe you are correct though.

[Nutz4sand]

Are you talking about making run the opposite direction for good? Or just for reverse?

The RER setups I have seen do not use the starter to spin backwards. They have a computer controlled igniton that actually sets the motor to a really (really) low rpm then fires a plug at a time to actually make the motor start running backwards from compression and spark. No starter involved to spin backwards. I have seen a few starter flywheels big enough to hit them in each direction but there are a few.

The drive clutch would be fine but the driven needs both ramps. Otherwise it will try to simply open up and not function right. Can pinch on the belt and stick.

I do not think cooling is an issue as the pumps are centrifugal and how far are you gonna back up anyways? Even if it did not move coolant well due to angled vanes I cannot see a person backing up far enough to get a motor real hot. (Plus on a sled with cooling tubes in the tunnel that require snow tossed on them for "normal forward operation" to cool the motor) You back up what ten feet? Normally. Trying to backup 1/4 mile might get a motor pretty warm in a sled with no snow tossed on the tubes. A radiator should eliminate this problem. 

I never thought about the oil pump before. Now I gotta go find out how they do work in reverse on an RER. 

We used to get old points motor bikes to start in reverse all the time.  I would be surprised if a common forward only CDI would spark at all spun the opposite way it was made to. The magnetic pulses would likely not be where they need to be over the magneto coils and moving to produce the energy when the trigger tried to sense crank position.   

[Boostinjdm]

[Boostinjdm]

  I would be surprised if a common forward only CDI would spark at all spun the opposite way it was made to. The magnetic pulses would likely not be where they need to be over the magneto coils and moving to produce the energy when the trigger tried to sense crank position.   

HE HE HE.  That was the very first thought I had.  But I think there is an easy fix.  A second trigger with a relay to switch from "forward" trigger to "reverse" trigger when reverse is activated.  Timing problem corrected and one cdi takes care of both directions.  In theory if the cvt worked you could go just as fast in reverse as you could forward with the same power.

The engine I have in mind is a reed valve engine and the starter is on the pull start side.  I figured maybe a second starter and a ring gear on the drive clutch would get er spinning in the right direction.  That would keep the weight and $ penalty to a minimum.  It would be better to figure out a setup to idle low and switch to the "reverse" trigger while running.  Then the weight and $ penalty would be almost nothing.

[Nutz4sand]

I think the comet has both ramps as those clutches get tossed in all sorts of things and you never know what side or rotation its gonna be on making it so they made them both.

As for the CDI and the switch thing. I dunno.

I like the RER idea but I would simply find a sled with it. And pirate that motor.

[Nutz4sand]

Side note. Sled reverse chain cases weigh about 25 pounds maybe. They shift pretty easy to if in good shape and aint that $$$ if you hunt around for one. I can find them for under $250.00 for the sled motors they live behind.

I plan to use them just like below. But I see no reason it could not be utilized in any buggy design.

I guess this is a lil hijack aint it...  :P

[Boostinjdm]

I would simply find a sled with it. And pirate that motor.

I would too if I didn't have a brand spankin new engine sitting on the shelf waiting for a project.  I'm pretty sure now that I am going to use it with or without reverse.  I'll just leave enough room for an upgrade later on.   If I could figure out a homebrew RER setup, that would make my day.

[Boostinjdm]

I don't mind a little hijack here and there, but I think we have enough FNR threads.  I would like to keep this one directed towards the RER or PERC concept.  As It could benefit many for minimal $$$ (hopefully)

[Nutz4sand]

The biggest problem I see with RER's benfit (Factory or your homade) in a buggy is no gearbox required but you STILL gotta do either a double jackshaft for enough geardown or a HUGE Pizza pan sprocket which totally screws ground clearance.

Unless.... You run the power to the front of the trailing arms (Supposing you use those) and run the chain back on the trailing arm to a big sprocket on each tire. Then you don't loose ground clearance in the middle.

[Boostinjdm]

I never said no gearbox.    Also, a sled box carries a weight and fitment penalty that a backwards running engine does not. That is still off topic though....

[b.c.bugger]

ok, thought I would throw my $.02 in here. Nutz has it pretty much right. You can theoretically run any 2 cylinder 2 stroke in reverse, but I don't think it's possible on a rotary valve (doo583 & 670)
Polaris and skidoo both make kits available to convert your late model twin to perc or rer
I am most familiar with polaris rmk so I will comment on that
Anybody can use parts from a 2003 or newer 600, 700, 800 perc motor and adapt a polaris liberty twin over to reverse rotation
OIL PUMP: The oil pump on a perc or rer equipped motor is made to pump oil while spinning in either direction. Most(me included) feel with a non perc pump they will not be in reverse for long enough to worry about missing any significant amount of oil. The bad thing is that if you have a non perc oil pump, it can actually pump in revers and start pumping air into the line from the injectors/ crankcase bearings. Not a big deal if you only have it in reverse for long enough to back up a short distance, then immediately put it back in forward
WATER PUMP: Not a big deal, it still pumps, although at a lower volume, but when in reverse you will not be revving the motor enough to worry about cooling. Just don't try backing up for 10 miles. There is no diff between perc pumps and non perc pumps
CDI AND RETARDED IGNITION IN REVERSE: You must use a perc ignition, there is no other way to make it work. yes, older points style 2 strokes would often start in reverse, but it won't work with a cdi sled motor
STARTER MOTOR NOT TURNING IN RIGHT DIRECTION: The starter motor has nothing to do with perc. perc works by slowing an already running motor down low enough, then firing far enough below t.d.c. to make the motor spin the other way. The motor has to be running in forward first. perc works with or without a starter, the starter has no effect on it
C.V.T. NOT FUNCTIONING: As stated, the primary works no matter what direction it spins. The secondary however has to have the helix cut in both directions. Doos and poos with perc or rer use a reversing Team rapid reaction secondary. It works every bit as well as a non reverse secondary and is a direct swap with no other mods