Predator 212 low compression

[cheetahgod]

The used go kart I bought came with a used predator 212. It ran alright stock. I removed governor, added custom exhaust, and mikuni carb. The motor seems easy to pull over. I checked the compression an it was about 30psi. The motor does run but requires the adjustment on the carb to be adjusted and many pulls to get it started. Also once in starts it revs up and does not idle.
Any ideas?

 

[OzFab]

When you removed the governor, was the camshaft removed?
When you put it back together, did you check that everything was where it's supposed to be (cam followers, pushrods, timing marks aligned etc)?
After reassembly did you check/adjust valve lash?

 

[cheetahgod]

The camshaft did fall out but I put it back in and aligned the two dots that is all

 

[Whitetrashrocker]

Take the valve cover off and check to see if the push rod came off the rocker.

 

[cheetahgod]

well i've spent $300+ on stuff so far...

 

[Whitetrashrocker]

Perfect. I've got 400 in mine . Buy that engine and your on par for the course.

 

[sefishy]

readjust the valve lash or put it back on the rods.

 

[cheetahgod]

Kind of a noob
How do I do that ?

 

[Kartorbust]

Get a set of feeler gauges and loosen the nuts on the rocker arms. Slide the proper gauge between the rocker arm and the valve stem, tightening the nut on the rocker arm until there is just a bit of resistance on the feeler gauge. Do this to the intake and exhaust valves. Plenty of videos on YouTube, Red Beards Garage has a video on modifying the 212 and I believe he does talk about setting the lash. I know for sure his 420 video has it and the concept is the exact same, however the specs may be different in how much the lash should be set.

I believe the lash is .005 (five thousandths) for intake and .007 (seven thousandths) for exhaust with a stock cam. Also the engine needs to be at top dead center (that is the piston is at its highest point) to set valve lash.

 

[bob58o]

I believe the lash is .005 (five thousandths) for intake and .007 (seven thousandths) for exhaust with a stock cam. Also the engine needs to be at top dead center (that is the piston is at its highest point) to set valve lash.

I had to look up the stock valve lash. It is indeed 0.004"-0.006" Intake and 0.006"-0.008" Exhaust.
https://manuals.harborfreight.com/manuals/69000-69999/69730.pdf

And remember to set lash at TDC when the Compression stroke is turning over into the Power stroke, not when the Exhaust Stroke is turning over into the Intake stroke.

Compression/Power TDC -valves are closed, Lifters on base circle. Set lash here.

Exhaust/Intake TDC -both lifters might be on the cam lobes instead of the base circle (if cam profile has overlap). Don't set lash here.

If you cant figure out which TDC is right by watching the rocker arms as you spin the engine, then inside the case... when the dots on the gears are aligned, you are near TDC of the Compression Stroke. This is where you want to set the lash for both the valves.

But since the Push rods look to be in place... I suspect the lash is ok.

 

[KingCobra]

While your engine was running, I was watching your rocker arms and everything seemed to be running smoothly and quiet...... But I got this headache now

 

[cheetahgod]

Why would I be getting low compression then?

 

[KingCobra]

Why would I be getting low compression then?

Are your rings or ring bad? Maybe the piston is warped from all that high speed running......... I've never removed a piston before in these type engines... only in V-8's etc. What exactly IS low compression? Have you compared it to another engine of the like? Maybe someone will pipe in and give us their compression answers. I gave my old comp tester away long ago. Are your valves leaking? Have you looked at them? bad seals?? I just don't know what else could be the cause of that except the piston or rings.

 

[Nosandwich]

How come nobody has mentioned the compression release?

I thought 30 was about normal with it in play.