robins 2 cycle rebuild ?

[moe3637]

ok been tryin 2 get more torque out of this lil 2 cycle motor 4 the woods 4 awhile now .....i checked comp 2day and it only has round 85 to 90lbs...is this ok ? if i build it should i go oversize or stay with stock ? how much over size is safe and what is stock size for piston .... oorrrrrr should i just go with stock piston and rings ? the cart still runs good. no smoke, starts right up but weak in the woods [pullin hills goin over logs ,so on and so on ]

[Dave Box]

90 psi is not the greatest but I think I would shim (or clock) the driven clutch first to see if that gets you better low end torque. It will cost you a few pennies to try as opposed to a few hundred to rebuild the engine.

Dave

[moe3637]

plz explain ? never heard of it... thks for the reply

[pachanga90]

The compression is at the bottom of the spec.Over-Bore is for wear,you won't gain enough to notice by boring it more than needed to clean up the cylinder.I found more power by shimming the Drive-Clutch(engine-clutch)3/16".It made a nite/day difference on low-end.It is still a 244cc. 8hp,motor,you aren't going to get much more from it.The timing needs to be set at or near 0 for it to be able to run in reverse,so plenty of availiable power is sacrificed there.The Port-timing in the motor isn't meant for high-torque,the carb.is undersized,and the exhaust is restrictive,and doesn't have a Power-Band to help build power.They will run good and strong on decent trails,hils kill them,especially long-grades.They just run out of momentum.I messed with mine for 4-yrs.until it was finally tired,and I swapped to a Big-Block.They are a good durable engine,but limited in power and improvements without spending a ton of money.Hope this helps.

[Dave Box]

Sure thing Moe, you said

the cart still runs good. no smoke, starts right up but weak in the woods [pullin hills goin over logs ,so on and so on ]

So basically the cart isn't in too bad shape and what you really want is more low end torque. The first thing that you should check is if the belt is worn as this will cause a loss of low end power, it is the width that matters so measure across. It should be 1 3/16 wide, much less than 1 1/16th and a new belt may cure your problems.

If it doesn't then the solution may be to get the driven clutch to open more slowly, this allows the engine to build up more revs and effectively provides more power at lower speed. There are two ways to do this

1. Clocking. This involves taking the clutch apart and rotating the spring to place it under greater tension. Here is a great video that explains the whole deal

secondary clutch disassembly clock - YouTube

secondary clutch disassembly clock - YouTube

2. Shimming. It may be that your clutch does not have the type of spring that allows for clocking, if so you can shim it by adding some washers behind the spring. This has the same effect by making the spring feel that it has more tension and thus causing the clutch to open slower.

There is another alternative which is to use a shorter drive belt. I have done this myself and it works however I feel that the correct engineering solution is to clock or to shim.

Does that answer your question?

Dave

[moe3637]

thanks fellas yal r awesome help i wil give it a try.. ive ordered the shorter belt that we talked bout in the other forum......u think i should order a 28 degree helex or will this b just as good ?.or even order another spring cause im sure its prob the 1 that came on it,,

[kantuckian]

Good info