212 hemi rpm problem

[N1YDP]

have a 212 with govenor removed, billet rod/flywheel,308 cam 26lb springs,.010 head gasket and 22mm carb.it wont rev past 4000 rpm in the mini bike on the road.on the stand it will rev to 7000 no problem.
do i need a bigger carb?it is running very lean

 

[anickode]

have a 212 with govenor removed, billet rod/flywheel,308 cam 26lb springs,.010 head gasket and 22mm carb.it wont rev past 4000 rpm in the mini bike on the road.on the stand it will rev to 7000 no problem.
do i need a bigger carb?it is running very lean

What is your gear ratio?

And if it's lean, jet the carb.

 

[N1YDP]

torque converter 12 tooth 54 tooth rear
it had a 85 jet.i put a 92 in it

 

[anickode]

Tire size? If you've got great big meats on there, the ratio might be too tall and it just hasn't got the oomph.

Or it could still be lean. Clean the plug (or install a fresh one), then run it and check the plug again for an indication. 22mm carb SHOULD be big enough if it's jetted properly, though there is a 24mm flat slide available, but that's getting up into the range where if you don't need that big of a carb, it will hurt more than help.

Is your timing advanced at all?

 

[N1YDP]

16" tire.no timing advanced.i just ordered a 26mm carb

 

[anickode]

16" tire.no timing advanced.i just ordered a 26mm carb

Or just spend money without actually figuring out the problem...

 

[mckutzy]

How are you checking rpm's...as in what device?

 

[N1YDP]

tiny tach.its what i used on my racing mowers

 

[bob58o]

You might want to advance the ignition timing.
What is recommended for your camshaft?

The gearing and tire size has you at 47 mph at 4k RPM.

A TC will increase RPMs from the point where it engages to the point where it starts to shift.
So lets say the TC engages at 2200 RPM and shifts at 4000 RPM.

RPMs will increase until the TC starts to shift, then RPMs stay "constant" while the TC shifts. MPH will increase during the shift, RPMs should not.

Then after the TC has fully shifted, RPMs will start to increase again (provided the engine has the power to continue to accelerate the vehicle in Overdrive). In overdrive your gear ratio is 4.05 :1. With 16" Tires you may not have the ooommph to continue to accelrate.

You may want to try to adjust the Driven Unit spring preload to the hole that gives the most spring pressure. This will delay the shift, keeping you in a lower gear longer, allowing more RPMs before the shift happens.

---------- Post added at 09:19 PM ---------- Previous post was at 09:13 PM ----------

Many have claimed that they have issues revving their engines using the 30 series TC with 6" driven pulley. People have had more success with the 7" driven pulley. I think the difference is in the gear ratio, not the pulley - but people swear that the 7" is better for revving.

 

[N1YDP]

maybe i will switch to a jackshaft

 

[bob58o]

My 30 series with 6" driven pulley had no issues revving to 7k RPM.
But I had 13.5" tires and something like 54: 8 for my sprockets. If you know the carb is lean, why don't you do something about that first?

 

[mckutzy]

Just spitballing here.... But are those cam and springs a good combo together?

 

[bob58o]

Just spitballing here.... But are those cam and springs a good combo together?

Good call.

Not the recommended springs or recommended timing, but I don't think a cam that asks for 32lb springs for 8k+ RPM will float the valves with 26lb springs at 4k.

I'd get a billet flywheel. Set it to 34 degrees. Get 32 lb springs. Fatten up the jetting. Change the gear ratio. Change the TC driven Preload. Perhaps look into a 7" pulley. Then look into a good clutch if still not satisfied.

The camshaft is for 8400 RPM. You are geared for about 100mph at 8400 RPM. You are not going to get there. Sorry.

 

[Joe-405]

It’s either timing - or jetting. NOT the carburetor.

Sounds like multiple issues to me.

 

[Jim289]

That's a gearing issue.

 

[KartFab]

timing wrong? thats for sure 32 dbtdc
jetting wrong, yes its wrong. try this http://www.nrracing.com/product-p/22mm-jet-kit.htm Fits Small Body Mikuni 22mm. Will not Fit Flat Slide or Large Body Round Slide.
Gas = 130 Main, 12.5 Pilot
Methanol = 210 Main, 20 Pilot
piston hitting head - possibly you need .020" from piston top to head.
wrong springs? yes, cam calls for 32 lb and you put in 26, you may be able to shim for higher pressure (e.g. spring install heigh is X and gives X pressure) this is found on the page you buy your springs from
wrong compression ratio - possibly. you can get a 11-12:1 compression ratio on that cam. if you dont have your compression and timing right, you may not hit those rpms
gearing bad? maybe, if your gearing is too tall, you will never hit the rpms you want if everything else is correct.
transmission bad? some say that the 30 series (esp with 6" driven) will RPM limit your engine. If you switch to a race clutch or centrifugal clutch you will not limit your engines rpm provided you geared correctly. Some people can set up their torque converters to spin 7k rpm.


So in addition to your problem (lean), you have other problems (see above). Good luck!