carlgrover

I am thinking about mounting a regular glow carb on this thing instead of the Walbro it comes with. I am having difficulty getting the left cylinder to stay lit when I advance the throttle. Has anyone tried this? It shouldn't be too hard. I will need to make an adapter for the intake manifold. I will use either a big Super Tigre or Perry carb.

pe reivers

I suggest You the regular MVVS carb of 8mm (#3219, 10-15cc). Of all carbs I tested so far on several engine brands, these give the best results in ease of adjustment, trottle response and clean running midrange.
The walbro is not particularly suited for glow fuel, so the change should improve things.

It pays to experiment with plugs on the cylinder that tends to flame-out. This is a common twin problem. To get both cylinders fed with the same mixture is nearly impossible, unless internal gas flow is mastered completely and the mix is ditributed evenly See the solution on the 116cc engine
So it pays to have a fuel with wide combustion limits (higher nitro content), and plugs that stay lit longer on the cool side that tends to flame out because it gets a richer mixture than the other cylinder.

carlgrover

Thanks for the help. I had previously installed an on board ignition system which hasn't helped at all. This is why I am thinking of using a different carburetor. If the throttle is advanced extremely slowly, one click at a time, both cylinders will somtimes stay lit. I think my problem is not enough fuel. The high speed needle on this carb does not work at all. The only adjustment that works is the low speed needle and that is very difficult to adjust since the carb has to be removed in order to get to it.

Rudeboy

You are partially right, the high speed needle does not appear the work. But the cause is actually the fuel orifice AFTER the needle: it is sized for gasoline and is too small for the huge amount of fuel a glow engine needs compared to a gasser. Drilling out the needle seat makes the needle more effective. After drilling I can now actually run my engine too rich.

Playing with compression and sleeve shims also helps a little in getting both cilinders balanced.

Other than that, follow PĂ©'s advice

proptop

My Feedback: (8)

I was just talking to a friend last week about doing something like this with mine.

I was thinking of using a large bore Perry pump carb. and a V30 pump.

I got my 1.20 twin for 50 bucks because the guy who had it had "had it" with the Walbro, and quitting on one cyl. etc. etc. I think the Perry pump/carb. should be able to flow enough fuel to keep 2 .61 size cylinders supplied, don't you?

If you go the ST or MVVS carb. route Carl, let us know how it works...

carlgrover

I looked at the Perry and a pump too. I really think this is the best way to go. The idea to drill out the Walbro carb is very good and I may try that too but that carb just wasn't designed for glow fuel and the gaskets/seals etc. will eventually go bad. I found a Supertigre .90 carb that I will try just to prove out the concept. If it works then I'll get the big bore Perry. I will have to make a mount for the carb to sit over the reed valve.

I did a large write up in either this forum or the MVVS forum on everything I have done to date to try and make this thing run better. If you are interested try to dig it up.

jaka

Hello!
Well these 1.20 and 1.44 twins must be MVVS's worst engines ever made.
I have had problems with these engines from the first moment I tried them several years ago. I have not been able to set them rich and the carb has been very hard to adjust properly.With Needles that don't respond like an ordinary glow engine carb needle. There are more problems to these engines but the above are some of the worst.
I have tried running 7mm, 8mm and even larger MVVS carbs, but this made no difference...setting the engine rich has still not been possible at full throttle.
I wonder if MVVS has given up on these engines?
Regards!
Jan Karlsson
Airracing products
Swedish distributor of MVVS engines

captinjohn

jaka: DO the Twin cylinder engines and the single cyl engines both have these problems? Thanks Capt.n

jaka

Hello!
No!
Jan K