Tweaking the Thumper

A assist with rope ratchet


--- On Wed, 2/18/09, jo3jo2003 wrote:

Terry Chad,
I've been dialing in the "Colorado Bullet Thumper 4stroke".Epoxy Gel and a new longer split fuel hose anchored the motor end of the throttle cable. It was moving around and preventing a true idle.The engine is max at 3800RPMidle at 1800RPMI can probably Pitch the IVOs more...BUT?Chad...how far can you pitch the IVO blades and how do you know when to stop?Can you "over warp" them and damage the system?Maybe I should learn how to measure the pitch just for the "pure research" as you put it Terry.I was glad to read about "belt Flop" on the slack side of the drive system. I've noticed some flop and wanted to ask how to determine correct belt tension. If I understood you right what I'm seeing is about normal.Last...Terry ....what do you think? The local Briggs & Stratton guys say I can install the high altitude carb kit in 15 minutes or less. I'm going to be launching from 8200+ MSL a few times this summer and the rest of the time will be at 5300 MSL. I'm thinking that it might be a good if I used Hi Alt jets here in Denver and the mountains and switched to the stock jets for the coastal stuff. These guys are willing to show me how to install and adjust them for the price of the labor Don't worry....Before I start changing anything I'll see how it does at the home field. But I wanted to run it by you.It's just too damn cold and the best I can do is tweak the machine.
JoeO

Hi Joe, I was thinking of you today.

I think 3800rpm is fine.

Belt 'flop' on the slack side is normal, but I find it's best not to watch it;); BTW, I have never lost a belt or even had the belt jump a groove. Belt tension is not something you need to worry too much about..tension it about like you would your underhood car belt. If the belt 'flops too much to suit you, tighten it a little more, you won't hurt anything (however it's probably just fine right where it's set now)

I don't know about hi elevation carb kit, but I am curious about it..I wonder what the kit includes? Smaller jets? Different air filter?
One thing that might help is to remove all the filters from the intake shell. Please let me know what you learn about the kit.

It's cold here too; I delivered a new unit to Indianapolis on Sunday and I demo'd it for the buyer; a 5 minute flight was plenty for me.

Terry