piston conversion

CLEMTOG

CLEMTOG

Hero member
I know that it "can be done"

but what I need to ask from the techno gurus is...

"will it cause any problems?"

I am building a 180 motor at the moment, it is (was)  with 80mm bores of course, but I am thinking about fitting a set of barells and pistons from a 1000 (75mm bore) which naturaly enough, will fit into the crankcase throats with ease, since they are factory machined for the bigger size, since the liner portion which "hangs" in the cases is not supported by the opening, should I do this, or is it asking for aggro.

The reasons behind it are that I am not looking for max power (or more importantly torque) and aftermarket pistons are a huge expense, which would leave me with a set of 1000 barells and pistons (factory) with low mileage and in excellent condition sitting on a shelf unused,I am aware that the cranks are balanced to different factors for the different pistons, but this has not caused problems when the conversion is done the other way around, but how about this downsizing way araound?
so go for it and be damned or not???
CLEM
 
Hi Clem,

my understanding is, that the maximum Diameter with the standard barrels is 78mm. 80mm will cause to thin liners and would need bigger liners. Bigger liners will need the crank case and barrels to be opened up to take the bigger liners

so - if you don't have the pistons yet, go for 78mm pistons. Still needs machining. Regarding unsupported lower end of the liners if you use 1000 liners in 1200 crank case, I can't comment.
 
Hi Clem - I've done this a few times before with no problems - why not fit a set of std 1200 pistons to the motor and sell the 1000cc barrels with pistons? - I've got a good set of  used complete 1200 std pistons if you need them - regards - Phil
 
Lothar, he wants to put 1000 barrels (and liners) in a set of 1200 crankcases.
The question is 'would the loose fit between OD of liner and ID of crankcase mouth give problems'.
 
Grant said:
Lothar, he wants to put 1000 barrels (and liners) in a set of 1200 crankcases.
The question is 'would the loose fit between OD of liner and ID of crankcase mouth give problems'.
Click to expand...

see my last sentence  ;)

Laverdalothar said:
Regarding unsupported lower end of the liners if you use 1000 liners in 1200 crank case, I can't comment.
Click to expand...
 
So why all the crap at the start of the reply??????  :-* :-* :-*
 
Hi Clem,
The crankcase does not support the liners, so whether there is 0.2mm or 2mm clearance it makes no difference.  If you have no alternative then it will work fine in my opinion, and I have heard of others doing this without incident.  However, a component swap as suggested by Phil seems the best outcome.  Regardless of the poor press it received back in the day, the 1200 is the better engine. :)
Cheers
SteveB
 
Grant said:
So why all the crap at the start of the reply??????  :-* :-* :-*
Click to expand...

I was bored, nothing to do, you know...  ::)

(simply was unsure what Clem wanted as there was no mentioning of a 1200 crancase, just a 180? engine...)
 
CLEMTOG said:
I am building a 180 motor at the moment, it is (was)  with 80mm bores of course, but I am thinking about fitting a set of barells and pistons from a 1000 (75mm bore)
CLEM
Click to expand...
The case rests for the prosecution m'lud.
 
I would think in the short term it would work, but over many thousands of miles/kilometres the barrel/head would walk and cause oil leaks due to it not being positively located.

                                                      Dave
 
Only issue as I see it would be to get the barrel in line with the crank  As Dave pointed out, the barrel has no positive method of location in this particular configuration.  Small spacers on 2 of the non-oil-transporting barrel studs should be enough to get everything lined up again.

Yeah Steve, the 1200 is a big softie... :D

piet
 
I have matching numbers frame and chassis for a 1000 triple, going spare.
 
I can lay my hands on a set of number punches and a grinder. :P

                                                                        Dave
 
I am both dyslexic and fat so I cannt even hit the right keys even if I knew which ones they were,anyway, I have sourced barrells and pistons of the 1200 variety so it wont happen.
CLEM
 
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