[MNellis]

I'm not much of a two stroke guy and being as this is a Honda Twins board I doubt many of you are familiar with big bore street 2 strokes.....but there are a few so I'll give it a shot.

I modified one of the carbs on my Suzuki T500 to accept a vacuum port (similar to what I did on the 450). The other carb already had a vacuum port that is used for the vacuum fuel petcock so I didn't have to mess with it. After it was done I attached my Morgan Carb Tune guage and started the bike. Given that it's a two stroke I suspected the vacuum readings would be lower but I was surprised that the guage rods hardly moved at all. I can rev it up slightly but the rods only show a slight reading as the motor is coming back to idle which takes a few seconds on the 2 stroke.

For those that might have some knowledge of 2 strokes and for those that might understand the theory on how these things work, do you think that what I'm seeing is normal?

I was able to kinda/sorta do a little adjusting and get it dialed in a little better than what it was but it was frustrating to do all the work to install the port and not have it work out.

 

[66Sprint]

Mike... One question first..... Is the T 500 strictly a piston port valved engine, or does it have reed valves in the intake?.......My question is because the vacuum could be "countered" by the transfer pressures if there is no actual "shut-off" between the crankcase and the carbs.......I'm sure there is SOME vacuum present, otherwise the vacuum petcock would be ineffective, perhaps your gauges just aren't sensitive enough.....
Hopefully Rick (RicH2) will pipe up....

 

[MNellis]

Mike... One question first..... Is the T 500 strictly a piston port valved engine, or does it have reed valves in the intake?.......My question is because the vacuum could be "countered" by the transfer pressures if there is no actual "shut-off" between the crankcase and the carbs.......I'm sure there is SOME vacuum present, otherwise the vacuum petcock would be ineffective, perhaps your gauges just aren't sensitive enough.....
Hopefully Rick (RicH2) will pipe up....

Yup, strictly piston port on these things. I know the guages are working fine and they do show a little vacuum and they worked fine on the GL when I checked it the other day. I know there is a lot going on in two strokes with pressure pulses and back pressure but I think you're probably right, it's just not on a scale that these guages are designed to work with.

 

[Bird76Mojo]

You may have to end up using a more sensitive (possibly electronic) carb tuning device. I bought a Twinmax and hope to have good results with it. I still haven't used it..

GB :mrgreen:

 

[RicH2]

I've always heard it doesn't work very well on a 2-stroke so I've never tried it. But, I would think the tune gauge just isn't fast enough to respond to the reversions that take place through the carb.

 

[66Sprint]

LMAO!......Isn't that what i said in layman's terms?..... :lol: :lol: :lol: