Gutted !

[highflyer]

Just finished restoration on my 250 2c and it will only run on one cylinder . After the usual checks ie fuel spark all ok I took the offending barrel off to find a gash below the bottom ring and part of the ring broken off There are bits or the ring in the crankcase and the barrel has a small gash too

Does anyone know if there are pistons available ?


It looks like it has a chrome bore Is this correct ?


Do I have to strip the engine to check for bits of piston ring ?

[Rick0705]

Sorry to hear that Chris,

Yes I would strip it as the smallest piece could wreck the internals if left. As for the bore it will need a re bore and it sounds like a nicoseal plating (looks like chrome) If you take the bores to an engineering firm that specialise in re bores linings ect they will have the parts required.

some one on here will know a reputable place near you,

Rotten luck Hope you get sorted quick.

[bantam1949]

Bad luck Chris.

The rings are a real pain to fit - you are not the first person to break one (or two!).

Pistons seem to be pretty freely available and the price on ebay has even come down in recent months. My 2Cs aren't nikasil so I'm not sure how you go about fixing the barrel.

Best of luck.

Tony

[Wards350]

Sorry to hear about the broken ring Chris. If there is a way you can account for all of the pieces when retrieved, I strongly recommend a tool I have made comprising a small powerful magnet firmly Superglued to a copper wire to go 'fishing' in the crankcases. Assuming the bottom end is all new it would be a pain to have to split the cases again or, at the very least, remove the engine and invert it somehow.

I have retrieved numerous items this way from some of the darkest (and oiliest) recesses!

Good luck.

Andy

[highflyer]

Thanks for your advice everybody .......... I have decided to do a full engine strip and re build ...........again

[ferret]

Hi Chris ,i agree its best to split the motor however i have inverted motors and flushed then out with paraffin then collected the debris and worked out how much was missing . I have just stripped my sons tdr 250 yam which was running great ,but upon removing the barrels you would question how it actually run and as well as it did , pistons all scored and chunks missing ,rings all grooved and evidence of seizures ,1 bore is nicasil the other has a liner fitted which has not had the ports profiled which is why the rings are so badly damaged ,the melted ali has coated the big ends oh and both heads are as rough as the surface of the moon , mind my benelli 1130 ran in a bad state and loads of internal damage .

[highflyer]

Hi Ferett .

That sounds like a viable alternative option . perhaps a good flush out with paraffin and using a magnet as suggested by Andy (Wards35 ) I have ordered a new piston and rings and I hope the bore is not too badly scored and I get enough compression for engine to run .

[R Powell]

Hi there just to let you know there are two types of piston for a 250 early ones with iron barrels have chrome rings and nikasil barrels have iron rings . Both pistons are available in 4 sizes on nikasil the barrell is marked a,b,c,d and has a different sized piston for each one these are sized by different colour dots on the piston. The Benelli manual has all the sizing details in it, the piston has to match the barrell!

[highflyer]

Thanks for the info Richsrd . My supplier is familiar with the bike as he has just sorted out the electrics and I am confident he will send the correct one

[highflyer]

UPDATE
I fitted the new piston at the weekend and the problem is still there .It runs fine on one cylinder but noticed no pressure on the RHS exhaust . After speaking on the phone to my expert he suggested the exhaust may be blocked . No way ! I have a set of brand new expansion chambers fitted that have been chrome plated and came nicely wrapped in newspaper . I removed the pipe and found a wad of newspaper in the system .After re fitting it started first kick.