Liners and Rebore

[moleymolo]

Been interesting reading on all the engine related questions and replies, but I have a few of my own

I have read that the CG10 and CG13 liners are all but 2mm.

So couple of questions:
1) Is that 2mm - piston - 2mm, or is it 1mm - piston - 1mm

2) are you sure there's a liner - just been to check the stripped engine I got and I can't see the join - normally you'd see a slight change in metal colour but I can't see anything - either meaning my engine has got a tapered top part of the liner making it hard to tell if it's got one, or the engine is that worn it's about to break?

3) Assuming it has one (which I'm guessing from the replies in previous threads - it has) would a new liner and a major rebore be possible - increasing the bore by 2mm? making it possible to fit a 73/74mm bore piston?

I await the huge amount of "do not bother reponses" :blues:

 

[frank]

the liners in the cg engines i,ve busted up were only 2 mm thick (75mm od) maybe the cga ones are bigger tho ?
if they are you could probably fit ga14 pistons eh (73.6mm)

 

[moleymolo]

Ok, looking overhead at the 4 cylinders. I've got about 7mm of I'm guessing engine casting inbetween each cyclinder. Does that include the liner? If it doesn't, skimming 2mm of each of the castings and getting new liners made up to fit - would that be feasible or is it a case of sticking with what's there.

From what I can see (and Ive taken some photos incase I'm getting confused) a definate 1mm off the castings with new liners is possible - but then again - never done it...

 

[moleymolo]

https://www.facebook.com/#!/media/set/?set=a.231979183499638.62249.227980427232847

 

[moleymolo]

As you can see from the photo (if the link works) theres 6/7mm of the engine casting before the piston - now I'm not sure if the liner is very visible to you in it, but I can't find it.

 

[frank]

yes about 7mm between the bores of a cga eh (8mm on a cg), so if you had a 1.6mm overbore on a cga block (.8mm off the wall) it would leave you with only 5mm of material, but i dont know how thick the liners are tho

 

[moleymolo]

So daft question now, are the liners you referring to actually the casting walls or are they added afterwards? It's so hard to tell with my engine - example 5mm of engine wall and 2mm of engine liner? or just 7mm of engine wall?

Giving the option to skim 1mm off the wall and replacing a new liner (custom made obviously) giving a new bore of 72mm correct? or going a bit mental and shaving 2mm off the wall and new liner giving 73mm bore?

From what I can see in the photo and this is probably just me being naive, but 2mm off the wall and a new liner doesn't look that impossible (of course the result will be if the engine works for a decent length of time)

I may have to pursue this...

 

[frank]

they,re dry liners (cast into the block, so if you wanted to go to a 73mm bore it would only leave a 1mm thick liner wall (too thin for cast iron )
so you could have the old liner machined out and a bigger liner inserted (meggabucks !) or else the cga is 1mm bigger (72mm) and if their liners are 2mm thick then a 1mm overbore (.5mm off the wall) would probably be ok (tho a 73.6 ga14 bore would be pushing it

 

[moleymolo]

Find me a cga motor and the parts to convert and ill do it... :blues:

Might enquire about the liners though - i know it's going to be a lot of work/money but I'm sure the end result will be worthwhile. Cheers

 

[frank]

Find me a cga motor and the parts to convert and ill do it... :blues:

Might enquire about the liners though - i know it's going to be a lot of work/money but I'm sure the end result will be worthwhile. Cheers

its just not worth it for an extra 50cc fwn far more gains to be had elsewhere

 

[moleymolo]

I suppose. Have just enquired about it to a guy who just PMd me on another forum so will see what he says.

Extra cc is always nice though.

Cheers for the help though.