My first project. Coborn?

Hi, I had a look at this engine on ebay. What you have there is a Coborn C6. A 603cc 6hp beast.. a friend of mine 'MakeDoAndmend1' has 3 Coborn engines, a C3, a C6 and another C3.

They made 25,000 of these engines..

Ill be able to pass on some lessons I learnt from mine, they have a cam operated oil pump and oil dipper for lubricating. The oil pump fills a try which the dipper then runs in. If the oil pump doesn't function the engine gets no oil at all. So I would advise taking the crank case door off and cranking the engine other to see if its working. The air vain governor at the back of the cowling is hard to set up, they run best when the throttle is locked closed.. has a Wico impulse magneto so it should start with a simple flick of the starting handle. Be careful of the handle, they have a tendency to stick and then be thrown across the garden. The engine runs a Solex carb. Those suffer badly with wear to the throttle shaft. If its worn it leaks air making it difficult to set up correctly. The carbs are also known to warp which has the same affect.

The exhaust is simple to replace. A 1" BSP £14.99 Briggs and Stratton exhaust can be had on ebay. Fitted to all 3 of my friends Coborns and they sound lovely.

The old C3 has a good heavy flywheel. So they can easily run at speeds of about 400rpm (not for a long period of time due the splash lubrication. So around a 1000rpm is a good running speed.

I see you got the C3 dimensions, which is probably why you were surprised of its size. As the C6 is much bigger then the 300cc C3.

Finally a videos of a slow running Coborn C3 (the C6 can also be found on youtube) enjoy.



Cheers, Dan

Thanks for the info mo3mini, much appreciated. I have found the 'pump in the sump' thingie, I did an off engine test in a tray of oil and all is working well there so far, I'll do a real visual check when I get round to filling her with oil, but cant foresee any problems. I have obtained a pepper pot type silencer from a local garden machinery guy and will hopefully get that sorted and fitted tomorrow. The carb is in very good condition and shows very little or no wear in the spindles and has been checked with a steel rule and shows no signs of warping anywhere so far *fingers crossed*  I understand about the poss starting handle issues and will make sure all is well greased before fire up time. I did try a few test swings last weekend while checking for sparks and managed to hit myself on the elbow with the handle as it released, causing a big lump, some bruising and a few choice swear words, the most painful part was that my dear wifey was watching at time and got the giggles at my misfortune . I'll make sure I don't do that again.
All in all she is coming on slowly but surely now, I have obtained some 1/4 inch copper pipe and will also make some fuel lines asap. My temp trolley gave up the will to live and went all wobbly on the TV stand castors, so I have knocked up a replacement using 100mm x 50mm pine and some decent 'heavy duty' flight crate castors (from my brother in law) so she's a bit more stable now.

Does look very nice.

she looks really good with that new trolley, are you going to stain or varnish it? Also what colour are you going to paint it?

Lewis, I may do the trolley in red cedar as I have some in the shed somewhere and then a few coats of varnish. The main tin work on the engine will be done in an orangey red to match the original colour scheme.
I've had a productive day today, I was up early and got the exhaust fitted and then made up some fuel pipes, I haven't done the 'wrap around' on the exhaust for paraffin yet as I'm going to use petrol only for a while - maybe later paraffin may come into play. I then decide to do an inventory check to make sure all the parts were present and correct, after being spread around in the garage for cleaning, they were all temp fitted to the engine when located and if I may say so.... she's looking good so far!
I filled the sump up with around 1.5 litres of Miller SAE 30 Golden Film and gave it a dozen or so turns on the handle and the splash tray filled up nicely .
So all in all she's ready to run, but not just yet  - I then stripped all the tin work down again in readiness for rubbing down and prepping for the paint job that is planned for next weekend.
New fuel lines
All dressed up and nowhere to go
Full sump
Cranked over and splash tray full

Really nice job!

Looks great.

She's coming on a treat  . My neighbour had a rummage around in his garage and came up with a couple of cans of red spray enamel paint and donated them to my project, it's not the exact colour I would have gone for myself but its good to see the tin work in a proper colour rather than red oxide or grey primer and shining at last, so this red will do for now until I can find something better.
The other good news is... it runs. A new ht lead, plug cap, some petrol and 4 swings on the handle and off she went. I was expecting a major handle swinging session along with a few swear words at the least followed by clouds of smoke, but she fired up fine. A bit of fine tuning is needed to get a smooth (ish) idle if possible. She jumps around a bit with the occasional stutter and bang, but a few tweaks on the governor settings and air screw should do the trick. I'm a real happy bunny now.
Pulley side
Flywheel side
My toys..... 3 cyls and 1800cc of fun.

That looks really good, shame about the tractor in the back of the last photo spoiling the view.... 

Have been a bit busy lately with work and other stuff, so decided to have a quick play yesterday and finish the beast off. The last (pinky) red has been resprayed in a darker shade and has come up nicely. The original makers instruction plated was well past it's best, but I managed to copy the details from a youtube vid and decided to make my own from some 0.75mm anodised ally sheet and some printed/laminated vinyl. I also cut out a copy of the original lettering that was on the engine when I got it. I used plain white gloss vinyl and I reckon it finishes it off nicely.... having sign making equipment has it's benefits.
I've have found the rough running is caused by the rubber wheels I have on the trolley, the engine bounces around and eventually gets into a rhythm where the fuel froths up in the carb and floods out of the main jet when run on a hard surface. When put on the lawn (with wifeys approval) and the wheels sink into the surface she runs fine and will settle down to a nice smooth(ish) idle. I've had a great time with this project and am looking forward to my next one..... watch this space

I do like that.

now thats a cracking job you have done there .

I do like the way you have made a new manufactures plate , sets it off now many engines will have plates like that . Looks like it should be just come from the deeler .

matt