Speedy-Gonzales

My Feedback: (202)

When converting the ZENOAH GT-80 to Rcexl ignition can the stock sparkplugs be downsized to CM-6's and still retain good performance. I am assuming all you have to do is put CM-6 boots/caps on the leads and thread reducers in the heads? I am wondering if the CM-6 plugs will reach into the combustion chamber to the correct depth for good ignition and/or if the compression ratio will be compromised to any significance.

I need to lose a little width between plug caps so I can keep completely inside cowl. All I need is about a 1/4".

Speedy-Gonzales

Truckracer

My Feedback: (19)

You can probably get the 1/4" you need by downsizing to the BPMR6F plugs with their associates slightly smaller caps. These plugs have the 5/8" hex compared to the normal 3/4" hex and they are shorter than the normal GT-80 plugs. Yes, I have seen the CM-6 plugs used but I have no experience with them in this engine.

Tony Hallo

I converted mine to CM 6 plugs and ran fine but really if you are looking for ultimate performace, you might want to look at other options. The other issue I have with the GT80 is the amount of fuel it spits out. After 1 season my airframe needed redone, I replace the engine with a D&B 5.1.

captinjohn

Speedy, how are you doing on the Kavan 50cc twin conversion? Thanks, Capt,n

Speedy-Gonzales

My Feedback: (202)

Capt'n,

I didn't know I was doing a conversion on a Kavan 50cc!!!!! Enlighten me............

How did your walbro WT540 work for you?

Truckracer

My Feedback: (19)

Yes, they do spit! I always thought a long velocity stack on the carb would contain the spit but never tried one.

Speedy-Gonzales

My Feedback: (202)

The spitting or "reguritation" as I call it...... can this be a sign off too much back pressure from a restrictive muffler system?

Truckracer

My Feedback: (19)

Don't know! None of my exhausts were overly restrictive so I don't think that was the case for my engines. I just considered it normal for a piston ported engine. All piston ported engines do it to some degree depending on the intake timing.

Speedy-Gonzales

My Feedback: (202)

I'll tell you what.......I would much rather deal with a little fuel in my cowl than have a set of reeds go bad. I think the easiest solution to carb regurgitation is to clean your engine and cowl area after every flying session.

My ZDZ's spit fuel and my Webra Bully's spit fuel.
My glow racing engines spit fuel.

Conclusion......I would rather have an engine that "spits" rather than have one "puke"!

Tony Hallo

The problem with the GT80 is that it spits right on the firewall, doesnt take long to soak the airframe.

w8ye

My Feedback: (16)

There msay be a problem with too much piston clearance on the intake side of one of the pistons?

The pistons of piston ported engines seem to wear a lot at the lower edge of the skirt on the intake side and if you run the piston until this area gets too thin, the skirt will breakoff.

tkg

My Feedback: (1)

Your turning it to slow. Regardless of the noise issue the engine is ported to run at a certain rpm.

Speedy-Gonzales

My Feedback: (202)

I believe this is a condition even with NEW engines right out of the box.

The Ghost

Why not just seal the ariframe with epoxy like we used to do. I seal mine with a coat of polyester resin. It stops or slows down any problems.
Cheers

Speedy-Gonzales

My Feedback: (202)

Agreed! I'll go for that.

captinjohn

Yup....wrong guy...it was a Galves in another forum. Sorry about that. The engine that was going to get the WT 540 got pushed back ...maybe next summer, Capt,n

w8ye

My Feedback: (16)

TKG says, you are not letting the enine turn up the rpm it is supposed to.

I guess I'm guilty of that too as I fly around half throttle most of the time.

apalsson

My Feedback: (1)

Tony, have you had a look at the alignment of the metering valve?
A metering valve that is too open (sits too high) often leads to the carb spitting fuel

Scota4570

Most of my conversion engines spit back out the carb to some extent. I play with them on a test stand regurarly and do not like my hand covered in stinky gasoline. I have found, adding a velocity stack will cure it. I make mine out of conduit of aluminum tube as needed. If you make it long enough it will stop the spitting up. It looks like you could drill a hole in the firewall box to allow the stack in. Make the hole significantly larger than the stack. Drill other holes in the side of the box to let air in. If you have something in the box it obviously won't work.

Tony Hallo

This is the reason this engine is only useful in racing!

Tony Hallo

I beleive slows down is more correct here,I findit impossible to seal, the bolt holes are the first to show problems.

Tony Hallo

The stock carb and the newly rebuilt SDC80 did the same thing. I used the W gauge to set the height.

mrdhud

My Feedback: (48)

Hello all,
I have a question about the GT80. Mine is vary hard to prim the carb with the choke closed it take about 25 turns of the prop to get fuel to the carb. If I cover the carb with my thumb it primes vary fast so why does the choke have that small area ground out of it?

BarracudaHockey

My Feedback: (11)

Mine pops in 5 or 6 flips, so either your choke plate isn't seating or you're sucking air somewhere.

Speedy-Gonzales

My Feedback: (202)

Can you run any size plug cap on a Rcexl ignition module? As far as I know you can but the smaller CM-6 plugs require a inline resistor right off the end of the plug lead since the CM-6 is not a resistor type plug. Other than that I am thinking the modules will work on any size plug? yes / no ?

I have a guy ( will not name names here ) who is telling me I will have to send my engine and ignition to him for the plug cap conversion which I think is pure BS. [:'(]