Nemett Bobcat 15cc

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Nemett Bobcat 15cc

This topic has 10 replies, 3 voices, and was last updated 15 June 2013 at 08:36 by doubletop.

Viewing 11 posts - 1 through 11 (of 11 total)

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9 April 2013 at 20:34 #116476
Neil Craigs
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@neilcraigs43644
Just a progress report have been trying to get it to run on petrol with out much success,changed over to gas(L.P.G.) and this is much better got it to at least run for a few seconds,now going to increase jet hole diameter and change needle,

Neil
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9 April 2013 at 20:34 #2373
Neil Craigs
Participant
@neilcraigs43644
11 April 2013 at 11:39 #116621
doubletop
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@doubletop
Neil

I'm looking forward to a video. I'm halfway through my Bobcat so confirmation it runs would be a bit of encouragment. Especially after one of those "I wish I hadn't bothered" weekends.

I had asked for evidence that the Northumbrian was a runner and ended up providing it myself. I still haven't seen others running.

regards

Pete
15 April 2013 at 13:11 #116943
Neil Craigs
Participant
@neilcraigs43644
Pete,

Yes I have had similar experiences with other projects and you keep persevering then in the end you have to re-design the thing, but on a cheerier note I am making progress with the bobcat it will run ¼ throttle with the electric drill turning it but as yet stops when a remove the electric drill, I have increased jet hole size by 20% this did improve the firing from the first time.be warned it pulls a bit of through the push rod followers,

Neil
21 April 2013 at 02:35 #117446
doubletop
Participant
@doubletop
Neil

I was thinking about your last comment about the oil through the cam followers. At first I thought it could be crankcase pressure but it you've done the breather that shouldn't happen.

I was doing the counterbalance weights yesterday and realised that the weights dip below the oil level plug so with anticlockwise rotation oil will be picked up and thrown straight up into the camshaft and cam followers. Looking at it, it shouldn't be too hard to install an ally baffle just below the camshaft to reduce the amount of oil being thrown up to the followers.

Pete
23 April 2013 at 13:09 #117610
Neil Craigs
Participant
@neilcraigs43644
Pete,

Sounds a good idea,I was contemplating increasing the wall thickness of the cam followers and fitting a oil ring, plenty of room for the push rods,

Neil
25 April 2013 at 00:24 #117743
Stich NZ
Participant
@stichnz
Neil

I completed this engine some months ago with no problems in getting it running. I am using points and a simple ignition system ,a 6 volt coil, 91 octane petrol and an OS 27 carb. My biggest problem was a bit of vibration which was overcome by increasing the weight of the centre counterweight. Oil around the cam followers is no problem if they are a neat fit in the guides , What oil I had at the beginning has basically gone since increasing the size of the breather hole .

Stich NZ
27 April 2013 at 22:33 #117964
doubletop
Participant
@doubletop
Stich

That's encouraging. How about some photos of your setup, or better still a video of it running?

I've also made my central balance weight a bit larger than those on the ends. I thought milling the bar to produce two half weights was wasteful so cut them in half with a slitting saw, to compensate for the slightly reduced height I parted one pair off at 9mm wide and another at 12mm wide and then split them in two. So I've got a spare 12mm weight.

Thanks for the tips on the vibration and breather hole.

Rockers completed yesterday, valves on the cards for today.

Pete
2 May 2013 at 11:03 #118291
Stich NZ
Participant
@stichnz
Edited By Stich NZ on 02/05/2013 11:04:13
3 May 2013 at 22:09 #118377
doubletop
Participant
@doubletop
Stich

Thanks for posting this. I can see from your other photos you must be a bit of a guru when it comes to I/C engines.

I see you said you were using an OS carb. It looks remarkably like the carb in the drawings. I did try to look up the OS27 carb on their web site but it wasn't listed.

I see you've rigged up some form of distributor any chance of a sketch or photos?

Where are you in NZ?

Pete
15 June 2013 at 08:36 #122298
doubletop
Participant
@doubletop
Finally got mine to run
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