Quantcast

Will a CarbMate work for 2-strokes?

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

13brv3

Well-Known Member
HBA Supporter
Joined
Feb 14, 2018
Messages
94
Location
Tellico Plains, TN
Greetings,

Disclaimer, I haven't had much 2-stroke experience.

I own a CarbMate, and I've used it a few times for a 912 carb sync. I recently acquired a plane with a Hirth F-23, and today I decided to sync the carbs. The primer port on the Mikuni looks like it should (?) be a usable vacuum port, so I hooked everything up, zeroed the unit, then ran the engine. Much to my surprise, the indication stayed dead center, and I know that's impossible. I tried pulling one of the carb cables to create an imbalance, and still it stayed in the center, so clearly the reading is incorrect. Next I removed a hose from the unit, and the indication went fully to one side as you'd expect. I can also feel pulses on the disconnected line.

Question is- Should this work, or is this a 4-stroke only device?

Thanks,
Rusty (putting on my 2-stroke dunce cap)
 

poormansairforce

Well-Known Member
Joined
Mar 28, 2017
Messages
1,017
Location
Just an Ohioan
Greetings,

Disclaimer, I haven't had much 2-stroke experience.

I own a CarbMate, and I've used it a few times for a 912 carb sync. I recently acquired a plane with a Hirth F-23, and today I decided to sync the carbs. The primer port on the Mikuni looks like it should (?) be a usable vacuum port, so I hooked everything up, zeroed the unit, then ran the engine. Much to my surprise, the indication stayed dead center, and I know that's impossible. I tried pulling one of the carb cables to create an imbalance, and still it stayed in the center, so clearly the reading is incorrect. Next I removed a hose from the unit, and the indication went fully to one side as you'd expect. I can also feel pulses on the disconnected line.

Question is- Should this work, or is this a 4-stroke only device?

Thanks,
Rusty (putting on my 2-stroke dunce cap)
It's a twin that has a common crankcase. There will be no difference between the carbs. Think of it as a big single with better balance. Using 2 smaller carbs gets better idle, etc.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
4,645
Location
NJ
I seem to remember a separate port I had remove a set screw and screw a barb fitting to hook up a mercury balancer on my motorcycles. Not familiar with that engine or that sync tool but I would think if the slides or throttle plates are not letting in the same amount of air into the engine your tool should show that.
 

n3puppy

Well-Known Member
Joined
Jun 25, 2019
Messages
152
Like poormansairforce said - wont work on the F23 because common crankcase equalizes pressure both sides.
Would work on a more typical 2 stroke like a Rotax 503 Etc. .

Need a tool that measures on the inlet side of the carb not the back side like the primer port.
The classic Uni-Syn (and current copies) should work on the F23 opposed twin
798C3CEF-3493-4DD0-B64B-9199B849D889.pngBE3624BC-176B-47D1-8C5F-1EA87288F425.png
 
Last edited:
Top