RE: McCulloch conversion info, Pics
 

The carb that is on the engine has a 7mm throat. I tried a 11mm carb, but it was too large and didn't work very well. If I could find a carb with about 8 or 9mm throat they might work better. The 7mm is propably pretty close, since the rpm continues to increase until the butterfly is fully open.

RE: McCulloch conversion info, Pics
 

Did any of you guys get one of these up and running for rpm tests? I'd be very interested.

The engine IS an echo design, manufactured until recently in Italy and assembled in Mexico. It has been used by McCulloch for many years now, and has been used on brands including Valex, Euromac and of course the McCulloch brand itself.

Parts are still available for some versions of this engine, there have been MANY changes over the years, including two changes to the ignition system. The pink/orange coil has been out of production for a very long time, the next one brought out was a cream colour (Italian) and in some cases a black coloured german coil was fitted. The latest coil used is a blue one which is made in sweden (introduced not long after Electrolux aquired McCulloch, and probably a Husqvarna or Partner part)
n.b. if changing ignition coil, please note that to change from an orange coil to the later ones, a change in flywheel is needed due to ignition timing.

The crankcase has also had several changes over the years, very old crankcases were designed for two needle bearings to support the crank, later they moved to a needle bearing on the starter side, and ball bearing on the flywheel side. during the '90s they went to a dual ball bearing crankcase, all are interchangeable (Crank seals are larger for the ball bearing type case) Around the same time as they moved to this new crankcase there was also a change to the crankshaft manufacture process, which introduced an extreme weakness, however this weakness only ever seems to show up in engines fitted on hedgecutters. The weakness caused the starter side of the crankshaft to shear off level with the web of the crank.

Several changes were made to the piston rings, single ring is the better, the double ring (very thin and brittle) has a tendency to seize up from time to time.

Carbs have been changed throughout the years, the main difference being the carbs with splines on the adjusting screws. Other carb settings are the usual 1 1/4 turn for both however to get one of the splined type running, the high screw must be at 4 turns and the low at around 2 turns.

There is also a 25cc version available, the only difference being the cylinder capacity.

The starter assembly was also changed, however as we remove these for gas conversions here, I wont go into that.

I see these engines on a daily basis in the summer months, some variants are bulletproof however some aren't. It is common to see an old valex branded machine in the shop for servicing, but yet the engines produced in the early '90s fitted on hedgecutters are all but gone from circulation. We still see 5 or 10 a year with broken cranks, which we usually throw in the trash.

I hope this is of some help to you guys!

I myself am thinking about a conversion however for simplicity am thinking of the MT270 because of the availability of conversion kits. However the MT270/320 only has a half crank which has me a little worried.

Anyone requiring unmodified parts for these engines, drop me a pm and i'll see what I can do.

/netsurfer

RE: McCulloch conversion info, Pics
 

netsurfer, that's some good info, I wish I would have had that when I was messing with mine. One of my flywheels had two key slots in it, so you could alter the timing just by moving the flywheel on the crankshaft. But with all of my swapping of parts, that flywheel may not have been compatible with the coil I was using. (even though it had two positions) I don't think I ever used a different flywheel because I spent time machining one of them, so thats they one I always messed with. I did swap coils, but I don't think I tried all combinations, so that could have been my problem. I finally gave up on it, (them) since the Honda 4 stroke had me so intrigued.