Decompresser stuck open !

[starman]

Hi,
my Greeves Scotish has a 198cc to 250cc Pearson (Ajax) head conversion.
Sadly the decompresser has seized open. Anybody got any ideas how I can free it ? Also to make matters worse the thread which the cable passes through on the side of the decompresser has sheared in half! I have been able to unscrew the broken thread but I am unable to obtain replacement. Does anybody know where I can get one from, or the correct thread size.
Andrew.

[riflegreen]

Far as I remember , the decompressor is 14mm plug thread & just unscrews from the head .

The block that the cable sits in unscrews from the decompressor shaft and you should be able to push the centre shaft out .

Alternatively , do away with the decompressor and just fit another spark plug in the hole .

Chris

[John Wakefield]

Decompressor

These people sell new ones (bit pricey @ £20) see http://www.villiersparts.co.uk/cable.html
Not sure who they are as their contact page does not give an address, but a Google search reveals its a man called George Shead of Birmingham, well respected in horticultural machinary circles apparently.

[whitehillbillies]

A mate got one of these for his Yamaha TY175. looks well made. I was going to get one for my TCS scottish. I will double check the thread size.

http://www.ebay.com.au/itm/NEW-ROYAL-ENFIELD-DECOMPRESSOR-ASSEMBLY-/220739558681?pt=AU_Motorcycle_Parts_Accessories&hash=item33651a5d19

whitehillbillies

[starman]

Thanks for your help. The original is prooving stuben to remoove especially as its partly recessed in the top of the Pearson / Ajax head.

[Rob]

Just a point to beware of. The RE type as shown opens into the exhaust port after the valve. There is a channel within the head from the decomp seating. I'm not saying it won't work on a 2 stroke, I'm just wondering how it would vent. I might try my spare RE one on my Hawkstone to see as I have a spare trials head with 2 holes!

Rob

[starman]

I have found the original compresser from the 197 head but it's slightly different from the one fitted to the Ajax / Pearson head on the engine. it has an additional hole in the side of it on the flange towards the bottom so not sure if I can use it.
Andrew.

[John Wakefield]

Decompressor

As long as the compression is released it will be OK, fit it & see. Some decompressors vented vis a small hole through the cylinder head & barrel into the exhaust port, rather than direct to the atmosphere. It may be one with this fitting.

[starman]

Thanks John.
Sadly I have been unable to free up the decompreser fitted to Ajax head although I have been able to remoove it, there was no washer but the decompresser from the 197 head had a split washer where the extra hole is. Should I use a washer or screw it directly into the head ?
Andrew.

[John Wakefield]

Not sure what you mean by a 'split' washer. But if the head you are fitting it to has the hole, fit the washer, if not leave it out
You won't do any harm. It will either work or not