Allotment Gardening Advice Help Chat

Chatting => Equipment Shed => Topic started by: ex-cavator on May 12, 2011, 16:00

Title: Carburettor set up?
Post by: ex-cavator on May 12, 2011, 16:00
I've eventually got round to getting my late 60's Clinton engined Merry Tiller Professional running but could do with some advice on the carb set up.

It'll start easily, preferably with the choke closed & will then tick over OK regardless of throttle setting. But the only way I can rev it is by opening the choke - by half open it's revving it's socks off and the throttle, although the mechanism seems to be working OK, doesn't do anything at all.

Any suggestions?  :blink:
Title: Re: Carburettor set up?
Post by: Gwiz on May 12, 2011, 16:29
Clinton engines where obsolete when I started working on machines, so I've only ever worked on a few.
Can you post some pictures? they might jog my memory. :)
Title: Re: Carburettor set up?
Post by: ex-cavator on May 12, 2011, 19:03
Thanks, Gwiz - will do tomorrow.

I guess there's an excess of fuel going through and when the choke when closed is limiting it on air, allowing it to tick over. I've wound the needle jet in the bottom of the float chamber right up to restrict the fuel as much as possible & this makes a slight difference - reduces the revs slightly & allows the throttle to make a bit of difference, but the mixture screw doesn't seem to do much. There's no adjustment on the float & it seems to be moving freely.

Worse comes to the worse, I can probably use it with the choke as a throttle, but difficult to control with a 3-position manual choke (no cable to play with), and it probably won't do too many rods to the gallon  :lol:
Title: Re: Carburettor set up?
Post by: smud6ie on May 12, 2011, 21:17
This is a clinton engine off an old auto certies bowling green mower,does the carb look anything like yours?

Title: Re: Carburettor set up?
Post by: Vit on May 14, 2011, 08:56
What is the colour of the sparkplug? For me sounds like main jet channel blocked. No the jet, but channel. Or semi-blocked
Title: Re: Carburettor set up?
Post by: ex-cavator on May 14, 2011, 10:31
Here's some piccies:






Smud6ie - looks similar, but not precisely the same.

Vit - spark plug is black, but not wet or oily.

Took it across to the plot last night just to try it out. Used a piece of wire to fix the position of the choke to give good revs - just slightly open is good, high revs but not excessive. Throttle makes little difference unless I open it fully, then the engine dies.

Machine ran fine for couple of minutes, which allowed me to see that it'll churn up the hard ground brilliantly, even with two pairs of tines on it, but then when the engine got hot, it died, and wouldn't restart. After a while to cool off it would start again, but only briefly. Only other problem was. it was spraying quite a bit of oil out the breather pipe.

I'll strip the carb down & give it a thorough clean & check, but in the meantime, any ideas would be welcomed?  :)
Title: Re: Carburettor set up?
Post by: Vit on May 14, 2011, 11:41
Main jet channel.

Black sparkplug - you nearly flooding, which is normal with closed choke, but when you open throttle, engine stops, because not enough fuel. Idle and high revs usually going thru the diferent channels.

So, you need to soak your disassembled carb in the acetone for a night, then blow all channels with high pressure. Even foot pump should be enough(i hope so  :blush:)

Oh, what is the story about air filter? If you tried without it on open throttle carb will not work proper - not enough difference in the pressure
Title: Re: Carburettor set up?
Post by: ex-cavator on May 14, 2011, 11:57
I hadn't put air filter canister back on because it's not got a filter element in it - I need to get one, just need to find the right one  ;)
Title: Re: Carburettor set up?
Post by: smud6ie on May 14, 2011, 13:04
If your carb has a float like the one I am holding then the fuel level is adjusted by bending a tab between the fulcrum arms.
Are there two strings of numbers from 1 to 8 on each side of the carb body where the float chamber contacts?

The inital settings for the two adjusting screws is one turn out from lightly wound in.
Make sure the drilling is clean on the side of the protrusion inside the float chamber where the main jet screws into and holds the chamber on,this is where the fuel enters for the jet to meter.
If its spraying oil from the breather pipe then there's a good chance the rings or bore are worn or if your lucky,its over full of oil!

Title: Re: Carburettor set up?
Post by: Vit on May 14, 2011, 13:40
Sometimes rings can stuck in the grooves
Title: Re: Carburettor set up?
Post by: Gwiz on May 14, 2011, 13:54
The symptoms would suggest worn piston and rings.
I would expect a quicker "dying" of the engine if it was only a carb problem.
It might be worth having a look on ebay for a replacement as the Clinton is so old.
Title: Re: Carburettor set up?
Post by: R Tallentire on May 14, 2011, 21:51
I haven’t had much to do with Clinton engines but even with worn rings the machine should tick over and rev up. Set the carb up as described by smud6ie and also check the governor vane is moving freely as the throttle butterfly is controlled by this rather than the throttle cable which just increases the tension on the governor spring. The engine cutting out after half an hour could be due to a few causes, the most obvious being the plug sooting up due to the carb problems. Or it could be plug oiling due to the worn rings, but the engine usually needs a fresh plug to get it going if this is the cause. Another problem could be a dying coil, though they tend to stop the motor after a few minutes. Check the plug is sparking when the fault is on to eliminate this.
I noticed that you have some other problems that need attention if you do manage to get the engine right. That new exhaust needs a ˝” BSP 45 degree male female pipe elbow between it and the block to direct smoke and heat away from the operator and the throttle cable.  It also needs exhaust locking rings, as tightening the silencer into the port works but it “grows” into the ally and won’t come out again when it need replacement. Finger tight then locked by the ring is the correct way to go. The belt guide is also missing, the clutch will drag when disengaged if this is not fitted as it makes the belt form a loop round the engine pulley but not touching it. As it is, the belt will drop into the pulley groove, snatch, turn, flick out and drop in again.
Title: Re: Carburettor set up?
Post by: Vit on May 14, 2011, 22:10
Oh, you don't have air filter at all, but trying to adjust carb   :blush: So... if carb is absolutely clean, your semi-opened choke working as "air filter" to the air flow.

About rings and piston - engine start, so it's not high priority problem. Just check compression.
Title: Re: Carburettor set up?
Post by: ex-cavator on May 15, 2011, 11:20
Many thanks for all the advice, guys - given me a few things to look at, but it might be a few days before I do. I'll report back in due course.

As for the rings, I don't think these are necessarily a problem - I almost certainly overfilled it a bit with oil so it's probably blowing out the excess. The plug isn't oiling at all, when the engine dies the plug is black but still dry.

RT - the engine dies after just a few minutes not half an hour - sorry if I gave the wrong impression - so it could be the coil. Though I did check the spark after it died last time & there was one, though I might not have checked it immediately, or it may be that the spark isn't strong enough to fire under compression - I'll check again next time.

I'm not sure if it's the right plug or gap - the guy I bought it off said it didn't have a spark plug so he took one off a motorbike. As we don't have a Clinton manual, would anybody like to hazard a guess as to an appropriate plug and gap?

Points about exhaust & belt guide duly noted. Also re: air filter - I'll get a filter element before I try to set up the carb properly. Smud6ie - yes, I see the strings of numbers you mention. I'll check the things you & Vit mention & set it up accordingly.

RT - this is the bit that's confusing me - the governor vane. What is it exactly you're referring to? The throttle cable operates a sliding bar with a spring connected to the throttle lever on top of the carb (see my last pic). However, there is another (return?) spring (not fitted in the photo) that attaches to the rear left of this lever that also connects to - what? I haven't managed to figure out what it should attach to, consequently the throttle will not close completely as it's still tensioned by the other spring, unless I manually close it. So, is there something missing?
Title: Re: Carburettor set up?
Post by: R Tallentire on May 16, 2011, 20:58
My instruction book does not cover your model but says that all plugs have a 0.025” gap, some engines use a Champion J8 and some an H10. My engine looks like yours and has a J8 plug. I haven’t had the fan cowl off to make certain that it has an air vane governor but I think it has so here’s how these governors work. A wire link goes from the lever on top of the butterfly to a flap or “air vane” inside the fan cowling. As the revs increase the fan blows harder and air pressure against the vane pulls the throttle shut. The spring between the sliding bar and the butterfly lever tries to pull the throttle open, at a certain engine speed a balance is achieved between the pull of the spring and the pull of the air vane. Open the throttle control and the spring will pull harder so it takes a higher engine speed to achieve balance. If the machine hits tougher ground the revs drop so there is less pressure on the vane and spring tension again opens the butterfly until the revs rise and balance is again achieved.