intake manifold?

[pianoman8t8]

I had to "upgrade" my intake manifold to fit into my bike frame, and I was wondering if it would affect the performance of my bike... I had to make it shorter, and from aluminum. I drilled the inner diameter to 21/32", which is a little larger than the hole in the gasket. Does anyone have any ideas or suggestions? the whole manifold from gasket to end that is in carb. is about 1.25" long. very short.

 

[etheric]

That may actually help you, since the old/stock manifold is ugly/rough and bendy. If you want to match the intake maybe you could weld on a washer so that the gasket isn't just hanging out there in the flow. I'm sure you've a good reason, but if you custom made it then why didn't you just make it to match up better?
I was talking to a gentleman who builds 50cc moped engines to race for a living and he told me that a 90 degree bend in an intake is equivalent to adding 2 feet to it's length. So removing even a slight bend may help dramatically.

 

[Guest]

You may suffer from vapor lock in the carb and have problems doing a hot start (restarting a hot engine). Performance may suffer a little, but prob. not noticeable, from air/fuel mix that is hotter.

 

[dave1490]

this is realy a ? off what rpm range you want{low=torque}intake short and fat for high rpm,long and thin for low rpm.you might find that you,ll loose to much torque and need a deeper gear 50 tooth.but a good combination that can rev the engine quickly to it,s power band will be a good acceleration machine.but then top speed shrinks and spokes break.mostly this has to do with flow and raming effect of the mixture speed.used to spend alot of time building small block chev,s one of the best way,s to make power was the cam,on these that =,s the jug,s timing.you wont get lift but will get overlap and duration.

 

[Egor]

Looks good. Heat goes up, but all the motorcycles do use a heat block. If you think you need one just find some H D P E "High Density polly Etheline" make a block. The port match will not affect these small low reving engines, you will need to do a lot of work to notice a difference. Look down the port with the piston a top, if you see the skirt in the port, well you get the point. All this is to keep these engines from going over the two HP. Look for a good carb that will help the most on a stock engine. Have fun, Dave

PS: Look at the ports on Vax Russian engine, thats what racing ports look like. Just a note: you can throttle a Two Stroke at both ends, another way to keep the HP down. IE bigger hole lets more in the other end.