Mcculloch ProMac 3600 Brush Cutter Problem

I have had several cases of lean seize from using old fuel which is why I asked if you had checked the piston through the exhaust port.
Ethanol is hygroscopic and if left too long in the carb will do more damage than in the pics.
If you are feeling flush and want to avoid the problems with ethanol you could always use Aspen.
 

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^Thanks! I hadn't even thought about the ethanol until I started wondering what was different.
I don't think it seized (luckily!) it'd just basically drop back to tickover. It's running as sweet as a nut now.
I wonder how much new machinery and equipment has been needed because of the need to be "green". And if the trouble it's caused and the new gear needed has been outweighed by the "benefits"
I'd type more, but the power has just gone out because the wind has stopped blowing! :LOL:
 
Dave54 said:
I've been using it for nearly an hour this afternoon Slight carb readjustment once it had settled, but nothing really.
It's been fine.
I suppose I've been messing about with engines on and off for nearly 50 years now, and that's only the third or fourth time I can remember something similar, that is an engine that seems to start and run OK but stops after a while.
Had a couple of blocked fuel cap vents, that Mini thing with the fuel pipe, and a duff coil (on a Mini again IIRC) that was failing when warm.

I wonder if this time it's our "old" friend ethanol. Here's my theory. Ethanol had evaporated, leaving 10% less fuel thus making the oil mix more than it should be. Hence causing the engine to run weak until it overheated and stopped due to fuel vaporisation.
I thought (with hindsight) that it was smokier than usual.
John might remember the dire warnings in "Motorcycle Mechanics" back in the day, about using richer oil mixtures than recommended in pre-mix 2 strokes due to the engine running weak.

If it was that, then it confirms my feelings about pretty well all the "green" solutions on offer. I'd rather use vehicles etc. 10% less than have something added to the fuel that causes all sorts of problems.
Click to expand...
When I first started taking this hallowed tome, it was 'Motorcycle, Scooter and Three Wheeler Mechanics' - which dates me nicely :eek:
John :)
 
I'd forgotten it was called that!
We used to read it avidly!
The, er, slightly worn, examples we mostly owned needed lots of "mechanics"
 
For sure, we tinkered and 'sorted' things until they were knackered - I got my first moped when I was 7 and finally crocked that by dropping a gudgeon pin circlip into the crankcase :eek:
Did me no harm though and certainly stimulated my engineering based future......much better than being welded to a mobile phone, these days.
John :)
 
I was older than that, just in my teens when i started messing with bikes. My old man was pretty strict though! he told me not to go riding motorbikes on the road. I think the first thing I rode was a Norman Nippy moped "over the banks"
There was lots of Villiers powered stuff around then (late 60s) cheap. The odd Honda 50 stepthough.
Take it apart to see why it works. . .
I think people were getting better off, and had swapped 2 wheels for four.
 
Most of the old British two strokes had the Villiers 6E or 9E motor....a grand old 'pop pop ' :D
Enter, stage left, my first road bike, BSA Bantam D7, DSW 944. Bless!
John :)
 
I had a Bantam. The crankshaft seals were shot though!
Mate of mine used to tune them. gave them quite decent performance.
Only sold the last Bantam a few years back. They're still pretty cheap even today.
The old Villiers offering were not designed for performance (shall we say).
Had various old small stuff on the road. An Ariel Colt (nice) A Tiger Cub (knackered) A Bantam (similar) A Zundapp Bella scooter (quite nice), and an BSA M21 Combo (great fun)
 
One of the original ' tuning' devices for the Bantam was crankcase stuffers.....basically filling in the crankcase to improve primary compression. In fact all they did was to reduce the volume of fuel that could be sucked in, so that was a non starter (probably literally!)
With me, it was the usual stuff....Ariel 350, Enfield Bullet 350 and then on to the Triumphs......trying to kid everyone that the clapped out 500 twin was in fact, a Bonneville :cool:
Happy days! I have a BMW 1200 RS now....an old fellas 125 BHP 'sports bike '
John :)
 
These bikes my mate used to build were beautifully "ported" and polished. They were a bit peaky, but as quick as you'd want to make a Bantam. Not so much top speed, but much better acceleration.
I had various better bikes after. MZ 250, Honda 400F, a Yam XS750, Suzuki 500 twin, a really nice solo M21 that I used round town and for work etc. and a 750 Bonny.
I packed in riding 20 years back though. Too many blind homicidal idiots down here, and narrow lanes with high stone "hedges"
That Beemer sounds a beast John!
 
Its not a bad bike Dave, 1200 cc liquid cooled boxer engine and more comfy than the head down, arse up 180 BHP bikes I'm used to.
Electric suspension - you dial in the weights involved, choice of 3 dashboards, sat nav, 3 settings ABS, tyre monitoring, cruise control et al......doesn't stop you having a flight over the hedge though :eek:
John :)
 
Has it got an advance ****** lever for the mag John? :LOL:
Joking aside. I'm out of touch. Heard of ABS on bikes. Tyre monitoring too. (although you soon know if there's something wrong in that department) Not heard about electric suspension, sounds OK if you regularly carry a passenger etc. The MZ had levers on the rear springs with "solo" or "passenger" settings which was handy.
Don't some bikes have airbags as well? I read something I'm sure. . .
 
With this thing, there's a handlebar switch with a spring logo, and pressing that gives you the option of single rider, single rider with luggage, pillion, with luggage and so on.
The engine oil temperature is constantly monitored and you don't need to use the clutch for up or down shifts once you are past second gear. Tyre pressures are constantly monitored, and you can select the road conditions which govern the throttle response.
No airbags on bikes yet, but you can get them fitted to your jacket!
John :)
 
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