That looks like an Amal MK 1 1/2 carb, with enrichment plunger. Not sure if the pilot jet in these is 'fixed' like the MK 1's or removeable....but the MK 1's are famous for blocking the pilot jet if left unused for some time.

All sorted, thanks to in-motion who supplied new carb jets and gasket set. Bike starts 1st time everytime.

Hi Bambam-n-chunx,

I have just got my hands on a Montesa Cota 247 with the frame number starting 21M26 something or other and am trying to gain more information and came across your post.

My carb too is a 627/450 and wondered if you have any more information about it and other parts of the bike as all the manuals etc. that I have found atop at 1975.

Any info you have would be greatly appreciated.

Thanks

Arfur

Hi Arfur

If you need parts for your Carb then try Burlen.co.uk where you will find repair kits for your Amal 627/450 for about £15 - £20

It should have 150 main jet, 106 needle jet, 35 pilot jet

As for manuals try a Search on the Montesa specific forum for your model which might give a link to a free download. The main manual will cover all models from Mk1 (1967) through to Ulf Karlson Replica (1978 ish) for parts, but workshop manuals tend to cover all 250's and 175 models.

Regards

Dave

Hi Dave,

Stripped the carb today and it has a 140 main jet, 35 pilot jet and could only find a U on the needle so no idea what size that is.

I guess the main being smaller will cause it to be lean on high revs?

Thanks

Arfur

Hi Arfur

The actual Needle should be marked with U and have 3 grooves at the top, the needle jet has the main jet screwed into it and has the larger hole in it. The needle and its jet can wear, but the pilot and main jets just get clogged up.

I ended up changing my main slide as it was loose in the bore , the needle and all jets and the difference was amazing, it went from running really rich and four stroking at revs to running sweet and pulling like a train through all the range. Well worth the £30 to sort it!

Dave