Cota 247 Running Lean and Overheating

[cedric van heerden]

Hi Stewart,
Your best bet for rings would be Southwest Montesa.
Regards Cedric

[keychange]

Cedric

A prompt but disappointing response :
Andrew,
No stock on rings at this time.
Regards, Jared
S/W Montesa

I have asked kevinbreedonracing.co.uk any other suggestions are welcome

Andrew

[brownie]

Andrew
http://cgi.ebay.com/ebaymotors/Montesa- ... 500wt_1182
don't forget your piston to bore clearance first
Ross

[keychange]

Thanks Brownie - I got them $32 AUD delivered sounded pretty good. Steve (the mechanic) reckoned I could get by with a hone on the existing barrel and the existing piston is standard - I re-checked the piston I have and it is 72.5 (and I have a spare std at 72.5mm so all should be good.

I'll call you tonight to let you know how I fared with the TY

[keychange]

I finally got the piston out - that gudgeon pin was sooo tight. Here is an image below of the exhaust side of the piston. The camera shows up the marks more obviously than the naked eye - the other side is smoother although see close up in next post. I also note that this piston feels much tighter in the bore - it sticky at several points.

[keychange]

the inlet side of the piston - close up machine marks disappear towards the top - is that normal?

[David Lahey]

The wear pattern on the piston look normal to me

The other things I see in your photos are:
The air filter has been well maintained
There are no signs of seizing

Photos of the carbon deposit patterns in the bore might provide useful information about how well the rings were sealing
Photos of the piston crown, spark plug tip and interior of the head might provide useful info about possible overheating episodes

[keychange]

The new rings arrived but they don't fit - they are much thicker than the orginal and won't fit into the cylinder ring groove - by a loooong way - the originals are .75mm thick and 2.5mm wide

Advertised as " set of standard size piston rings to fit Montesa Cappra, Scorpion, Cota models with 72.5mm bore"

Anyone interested in some heavy duty 72.5mm rings ? These are 1.5mm thick and 2.85mm wide

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Update - TriCub tells me that my rings are not too bad and that they would not be producing the problem. So back to drawing board.

I will reassemble the engine and who knows maybe in the act I might plug a previously unseen gap. I realise now I should have kept a clear diary as I have made so many changes and reversed so many that now I am completely at a loss as to where everything stands. So it's everything back to standard and start again - fingers crossed.

I would say to all of you 247 owners with "wire rings" 0.8mm thick they appear to be as rare as... so if you find any - grab them now while you can.

Andrew

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Put everything back together and again cleaned all jets and set needle at highest position. Adjusted idle and mixture to get a reasonable idle- I then ran the bike at trials pace over logs etc for 15 minutes well and truly warm - engine was idling probably 300 rpm higher than to begin with. The picture below shows the plug which was brand new B7HS

So I went back through the old carbie parts the old main jet is marked 150 but on closer inspection it is significantly bigger and would appear to have been drilled (which was going to be my next move) so I installed the old one and now having trouble starting as the plugs appear to be loading up (good sign) and I am all out of new plugs . I'll let it rest for an hour and see how I go,