What would this do?

HuskieMobileMan · Post by **HuskieMobileMan** » Fri Apr 13, 2007 9:26 pm

If you take off the intake manifold and reed valves, there is a split going into the crankcase. Would removing the split making one entrance into the crankcase instead of two give you better crankcase breathing? Could it be bad for the engine?

Both my SE50 and NH80 have this split so I assume a spree would as well.

HuskieMobileMan · Post by **HuskieMobileMan** » Sat Apr 14, 2007 10:03 am

Any idea on this? I did this an now my NH80 won't run properly. Want to know if I need a new case or not.

MySpree · Post by **MySpree** » Sat Apr 14, 2007 4:58 pm

i always looked at it, but never dared to try it. try upjetting..

HuskieMobileMan · Post by **HuskieMobileMan** » Sat Apr 14, 2007 5:45 pm

MySpree wrote:i always looked at it, but never dared to try it. try upjetting..

I know the thing about removing the oil pump and changing the crankcase volume, but this seems like such a small change and right at the intake manifold.

When I pour a little oil in the crankcase, it runs pretty good for a while, then dies. I have an OKO 24mm carb on it with a 100 and 118 main jet. Neither of which gets it running. The slow jet is 42 I think.

My advice: don't do it, lol.

Why would it work with oil in the crankcase?

MySpree · Post by **MySpree** » Sat Apr 14, 2007 7:27 pm

i guess that makes the case volume go up.

Kenny_McCormic · Post by **Kenny_McCormic** » Sat Apr 14, 2007 7:41 pm

split the case and put a bead of allumiloy in there to up the volume. that should get ya going again

HuskieMobileMan · Post by **HuskieMobileMan** » Sat Apr 14, 2007 8:17 pm

I think I am going to get a used crankcase instead. I am also going to rebuild the bottom end due to some piston slap I am getting at idle. (I have already done the top end).

What all should I replace? Crank bearings and what else?

burnt_toast · Post by **burnt_toast** » Sun Apr 15, 2007 1:44 am

bearings and all seals.

Post by **noiseguy** » Sun Apr 15, 2007 3:44 pm

If you're getting piston slap, check your rod bottom bearing. That may be out, and is difficult to replace (most guy buy a new or good used part instead.)

Not sure what removing that web would do... you would still have the restriction at the reeds so I doubt it would help much. It would definately impact the structure of the case, though. Better time spent finding a larger reed valve assembly for your engine.

HuskieMobileMan · Post by **HuskieMobileMan** » Sun Apr 15, 2007 5:47 pm

noiseguy wrote:If you're getting piston slap, check your rod bottom bearing. That may be out, and is difficult to replace (most guy buy a new or good used part instead.)

Not sure what removing that web would do... you would still have the restriction at the reeds so I doubt it would help much. It would definately impact the structure of the case, though. Better time spent finding a larger reed valve assembly for your engine.

Why is it difficult to replace the rod bearing? Are the two parts of the crankshaft pressed together or something like that?

MySpree · Post by **MySpree** » Sun Apr 15, 2007 7:44 pm

yeap, you need a press made to take it apart, i made additions on a lathe that fit on the press at my dads shop so i can change them, at this moment the press isnt hooked up since they moved shops, but it should be up soon.

Post by **noiseguy** » Mon Apr 16, 2007 8:43 pm

Taking it apart with a press should be straightforward. When you get it apart, you have to get it back together straight. That's the part that I'm not clear on how you do... If anyone can fill me in on that part, I'd be interested...

Did you make a fixture that holds the crank halves in place (cocentric) while you press them together with the rod?