2013 Massimo MSU 500 Weak

[Redneck Mech]

I have a 2013 Massimo MSU 500 project. I just recently got it running after sitting in pieces for an unknown amount of time. I replaced the wet clutch and drum, the primary clutch and belt, the spark plug, ignition wire, and ignition coil. I cleaned the fuel tank, replaced the fuel lines, fuel and air filters. I adjusted the valve lash and  the throttle cable stroke. Now to the problem. It tops out in high gear at about 4400 rpm at 27 mph. It tops out in low gear at 5200 rpm at 28 mph? It will rev to about 7500 rpm in neutral. I'm guessing I just don't have enough horsepower for some reason. Ideas?

[T-boss 410]

Do you know what the factory hp rating is? Sounds like you already covered a lot of bases, as well as sunk some $$$ into it. Have you done a compression check?

[Redneck Mech]

No, I picked this thing up for $50. It's the first SXS that I've ever had. Just trying to figure this thing out as I go. No manual or anything. I've got to dig out my compression gauge. It's in this shop... somewhere. lol

[Redneck Mech]

Here's a "before" pic

[T-boss 410]

That's what you started out with? I'm impressed! I believe you can find a manual for it here on this site. There's a forum specifically for manuals. That will be very helpful.

[Redneck Mech]

Yeah well, I figured for $50 it'd be worth a shot. I'll do some digging around on this forum and see what I can find. Thanks!

[Alex]

Topic moved to Massimo UTV forum. All manuals should be located in downloads: https://www.utvboard.com/files/

[Redneck Mech]

Thanks Alex. I was going to post it here to begin with but there doesn't seem to be a lot of activity in this area.

[Redneck Mech]

Update: I just ran a wide open throttle compression check and it's 135! According to the stats that I dug up it's supposed to be between 163 and 210. So, that's not good. Also when I removed the spark plug it was chalky black with soot. So I've got something else going on, I'm not sure what yet. Grrrr!

[T-boss 410]

Bad rings, warped head, blown head gasket. Does it smoke much when running? Sounds like oil getting past the rings, maybe. If it does smoke, what color is the smoke?

[Redneck Mech]

Doesn't smoke at all. Just very weak.

[Redneck Mech]

I'm starting to wonder if one of my sensors is bad. The only new one on it is the O2. It's got a new injector so I'm assuming it's not causing the rich condition.

[T-boss 410]

How would that affect your compression?

[Redneck Mech]

No, it wouldn't, but I don't think the low compression would cause the spark plug to soot up. That's a definite sign of running too rich. If one of the sensors is sending an erroneous signal to the ECM it could cause it to run rich.

[T-boss 410]

Could a valve not be seating? That would account for the low compression. Too much air would cause the sensor to add more fuel, hence the rich condition.

[Redneck Mech]

Well now, that's a good thought. Tomorrow night when I get home I'll redo my compression test and this time I'll add a little oil. If the compression improves, it's rings, if not, it's valves. I new that just didn't think to do it. Thanks!

[T-boss 410]

Let us know how it goes.

[Redneck Mech]

Okay, so I'm in the process of rebuilding the top end of this machine and I can't find any timing marks on the cam. No notch, no dot, no painted tooth, nothing. Does anyone know what it's supposed to look like?

 

[TapBoss]

Does this help?

[Turkey 20k]

I have MSU 500 with compression being low also. When you say to add oil are you pouring a little oil in the plug hole? Thanks