WOT

Minimichael

Minimichael

Well-Known Member
#1
#1
How many out there are so well tuned they can reach for WOT from a dead stop? And just hold on then and climb through your rpms – without bogging or gasping? No feathering of the throttle to get thru those rough spots?

I'm getting close with my latest build, but admit each of my other 3 bikes call for a little wrist work here or there.
 
B

BrownStainRacing

Well-Known Member
#2
#2
Minimichael said:
How many out there are so well tuned they can reach for WOT from a dead stop? And just hold on then and climb through your rpms – without bogging or gasping? No feathering of the throttle to get thru those rough spots?

I'm getting close with my latest build, but admit each of my other 3 bikes call for a little wrist work here or there.
Click to expand...
I'd say 90% of the time, I can.
If it doesn't, theres usually something internal.

I've seen 5 or 6 heads in the last 4 months that had leaking valve seats. They still started and ran, jus low on power and sluggish, no tuning could fix it.
They were OHV clone heads, and lapping the valves solved the problem. Some took more time then others to get seated.

I'm working on a head now thats got SS valves in it. I think the valves have really messed up the seats. I got new stock valves coming, but I still think both sides will leak. It's ashame the customer had the head shaved and some other work done to it last winter, now the seats need replacing.

I put a used 20cc head on it and it hauls the mail and more. But his fancy, high dollar head is way down on power and all it is, is the bad seats.
 
Minimichael

Minimichael

Well-Known Member
#3
#3
That's food for thought that I hadn't thought of, and had me thinking about my Briggs 8B and how the valve stems are pretty loose in their guides. I guess internal damage or abnormal wear can occur pretty quickly?

Thanks BrownStainRacing. Of course, I'm sitting here with slide carb on the brain. Thinking about needles and signals and aspirations, as usual.
 
sparkwizard

sparkwizard

#4
#4
Governed engines do not seem to bog as bad. That is why we leave the governors in and tune the stock carbs. A couple of my engines have holes drilled in the governor weights, but they are still governed. We can yank throttles wide open and hang on. Bog is a lack of vacuum in the intake. Too much air, not enough fuel. Biggest most obvious reason for bog is too much throttle opening for RPM. Smaller carb does a good job of keeping operator from inducing bog.
 
SAS289

SAS289

Well-Known Member
#7
#7
I did one blacktop run like that on Friday. But did a slow roll then full throttle until top out.

Not into top speed stuff but was interested in top speed RPM. The tach already had 4550 max RPM recall from a full throttle off road. Interesting thing was that after the top speed run the max RPM on the tach didn't change. I got more RPM in the middle of a field than I got on the road which I'm fine with. All that is is the OD from the torque converter, gearing, and 196 power at that RPM range. With different gearing I got higher RPM and road speed with the same engine.
 
Minimichael

Minimichael

Well-Known Member
#8
#8
Skipp said:
I have a few that will….mostly hot rodded hs 40/50s with a mikuni….

have you honed out your ports?
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No porting on this one yet. In fact I shouldn't even call mine a "build." This one I'm referring to is a stock 5hp with a goofy 10" manifold and Mikuni and flex-pipe header. And I seem to be finding all my successes by just tweaking the needle shape. Of course, jetting choices provide the foundation, and while I found jets could smooth out and bridge certain areas along the throttle, it can also make other areas suffer. So now I'm back near stock jetting. The stock needle lets the machine fall flat on its face half way up the throttle. And a quite non-stock needle (one that's on the rich side early, and the lean side late) appears to be the whole ballgame.

And yeah, sparkwizard, I hadn't thought of the whole governor thing either. But I have been thinking a lot these days about vacuum and signal. (aka: learning the hard way) And certainly, wot is just one position. So, notwithstanding obstructions or other malfunctioning internals, I guess I should have asked: can you reach for any point on the throttle and get a clean, climbing response without any faltering of the combustion cycle? (Considering any carb type here, but no governor)
 
Minimichael

Minimichael

Well-Known Member
#9
#9
Cool, SAS289. And that's a whole other part of the equation, right? How big is your engine, rider weight, the incline, and what kind of gearing kit is in place to help a neighbor out.
 
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