LR1 Won't start

[Avondale]

Thanks

The supplier of the cylinder has indeed confirmed that the dims are incorrect and has suggested it be machined to match the original. It would appear to have been manufactured incorrectly and not to the original tolerances

Original drawing attached

Peter

[AdeV]

Good news! (kinda  )

If you can't find anyone local to do the machining for a decent price & you've not got facilities to DIY - I'm happy to have a go for you, gratis. Unfortunately my surface grinder isn't recommissioned yet, so I can cut it down to size, but it might need a little manual finishing with some sandpaper to get rid of any machining marks. Probably not necessary on an LR1... I'm based over in Birkenhead (CH41 postcode). It'll give me a good excuse to clean the machine up and re-tram the head....

[cobbadog]

I think it would most unlikely that the piston was machined to make it too short as that means the top of the piston had to be machined and that would possibly mean you would machine through the top of it. Compression is everything on a diesel and if they are at the lower end of a workable compression ration loosing 2mm of compression is devistating. Glort what was the reason behind removing 5mm from the head of the Victa head? To improve the compression ratio. Why? To gain power, do the reverse and the reverse happens and to the point it is like removing the rings from the piston.
To make the changes to the bore it all must come off the bottom of the bore as you will loose the lip for the head and gasket and it wont seal. Right now you need to re-assemble and accurately measure the clearance you have now to establish exactly how much needs to be machined off the bottom, then get that amount removed less the bump clearance. Any machining off the bottom will not have to be perfectly smooth if this uses a gasket on the bottom as that will take up any minor imperfections. This gasket must also be included when making the critical measurements to get the correct bump stop gap.
There should be no need to machine the head unless there is a known issue with it and if that is the case correct that first then do the test for bump stop gap as described above.

[Avondale]

Gentlemen

Firstly, thankyou for all your very useful advice. Much appreciated.

I had the bottom surface of the cylinder machined to the correct and original tolerances and re-assembled the engine with a re-con fuel pump and injector. I checked the bump-clearance which is now 'bang-on'

After priming the fuel system the engine started first time ! Whoop !

It runs fine, but it seems to be 'hunting' - slow and fast, slow and fast.

Any ideas?

Peter

[cobbadog]

Well done on getting it running again. The first thing I would look at is the governor to sort out the "hunting" on the revs.

[cobbadog]

Good points Glort, look at videos and I have found YouTube good for helpful tips and governeor springs can be a right pain in the rear end. I was going to mention mowers and the springs on them. I have a few different mowers in the collection and they all behave differently. One in particular idles as slow as possible and as you increase the revs it runs beautifully, but it's mate never does what I want it to until I bought a new spring and that helped a lot. I guessed that at some stage the original spring got stretched or loss tension and the new one sorted it. I also had a Suzuki 2 stroke that the governor was playing up and in that case it was poorly adjusted and a video clip showed me the correct way to sort it out and all is good now.
So keep on checking you governor, we feel your problem is there.

[listard-jp2]

During the rebuild, I fitted a new cylinder due to excessive wear of the old one.

It is just possible you have fitted the piston the wrong way round (the combustion chamber is offset, and it can go in one of two ways) OEM pistons are always marked on the crown which side faces the camshaft.

If fitted the wrong way round, it will create the exact problems you are experiencing.

Don't ask how I know