There are several chainsaw motors that have forward facing carbs and rear exhaust, or vice versa. Are there unsurmountable problems with the carb facing forward? These would fit well in a narrow cowl.
Thanks, motorhd

I think your refering to the Mac31cc,has a front facing carb.I had one but tossed it in the trash after taking the carb off.It had roller bearings on the crank and youd have to make a bushing or thrust washer to keep the crank from pulling on the case.May not be hard but not worth the trouble for me i quess.Plus youd have to come up with a mount system if i remember right.To many easier and workable solutions here in the forums.Plus the ones here in the forums are proven winners because a lot of us are using the same engines.

I don't believe the forward faceing Car. would be that much us a problem as far as air flow goes.

Glows have forward faceing Carbs. and they do okay.
You may need to run a line from the back diaphram into a dead air space for reliable Carb. tuning.

Also if I remember right there is an issue with the Carb. being so close the the prop.

I don't know about a thrust washer, but Buck has been there and done that.
Homelite, Poulan, Echo, Ryobi and Stihl are the main ones and not to many of the Stihl, probally because of the cost.

Just go to a small engine shop and tell them what you are doing. They will probally give you a couple of projects.

I was amazed at how many good engines are in the scrap bin.

Your right about the carb Ralph.I was making a mount for the carb for that 31cc mac out of aluminum to replace the rubber boot,plus i was going to use a 1/2 inch G10 board spacer as a heat dam.By the time all this was on there including the carb, the hub in my opinion would be sticking out far enough that the load placed on the shaft and front bearing swinging an 18 inch prop would be not to safe.


Motrhd,Again i agree with the engines that Ralph posted.Theres a load of us on here that run all those listed and theres threads devoted to each one.My self and only a couple more have ventured into the stihls.Not easy to come by and pricy sometimes just for a shortblock.The deals are out there,just have to think where to get them.Do you have a thought or vision of somthing you might be wanting to do so ya just need a starter project,or a particular plane?

Thanks Buck

I like to reverse engineer.
Start off with a plane. Find someone who has built one.
Find what motor they used and if they added any extra weight to the front to balance it.

Did they move the battery and servos to the rear?
If so how much weight difference did it make?

Moving the electronics to the rear means you can hang more weight on the firewall.
I've also extended the firewall to reduce weight.
One inch saved me 1 1/2 pounds of lead on a 1/4 scale cub I had my 25cc Toro on.
It looked like a Super Cub and flew a lot better a pound and a half lighter.

Ask around RCU has excellent records on different planes and what engines people put in them.

A little research can help you build an airplane that is heads and shoulders above the rest.
I find it exciting