cylinder bores

[nef1000]

hi.
could do with some clarification/2nd opinion pls.
i stripped + put back together ma10 recently. new head gasket set and reground valves.before stripping, cyls 1+2 had no compression, 3+4 ok. after rebuild, 3+4 excellent , 1+2 poor but better than before, car is burning oil really bad all the time especially under heavy acceleration. did teaspoon of oil test, compression improved so i guess rings are shot. took engine apart again to do rings, measured bores, sideways, all cyls are still at 68mm dia. front to back, they seem to have bored themselves to 68.20mm. haynes say 68.04 max.(i think) i have concluded the engine is shot and dont want to bore it out and line it. has anyone had similar situation. am i over worrying ie will new rings be ok or has it gotta be bang on.you know how sometimes haynes is over the top!!! gettin a new engine is no prob as i can get them free from scrappy but i dont wanna be opening them all up to find all ma10 are the same.sorry for the long post. any help appreciated.
cheers ne.
ps this engine has had 4years rallying so i am expecting worst for it!!!:down:

 

[frank]

ne

we get the same with our kart engines, if you dont keep the ring-gaps in the exact same position, a previously ok engine will lose compression and start smoking.
the only cure is new rings (preferably oversize ones, with the gaps filed to suit the bore wear) and a good glazebusting of the bores

 

[nef1000]

cheers frank.
so are you saying that block would be reuseable?
prob is i can only find standard rings for sale.

is the 68.20 dia acceptable? the wear is all gonna be at the front of the cyls from the force of the piston pushing up. can a pear shaped cyl be cured with o/sized rings?
it might be worth a new engine if a good one is likely to have perfectly round bores
cheers ne

 

[frank]

ne

.2mm aint a lot eh, a good honing and standard rings should be ok, i would have thought, you,ll just lose a tiny bit of compression down the ring gaps i suppose (we aim for a 10 thou gap on our 270cc singles)

 

[Ceirwan]

Don't know when it comes to engines, but when i was learning to be a fitter if i'd told the instructor that a .2mm gap wasn't much he'd have have gone mad at me! Surely if at all possible you should file them down as frank said, is not to difficult with patience to work to within 5thou when filing.

 

[Ed]

MA series engines are known to have oil burning issues after a head gasket change, carbon fouls the ring lands causing poor compression and oil burn. Also nearly all MA engines go oval, even the ST with much thicker bores.

I would try glaze busting the block and fitting new rings, chances are any MA engine you find will just be the same.

 

[nef1000]

cheers guys, thanks ed. thats exactly what i was hoping to hear. i either wanted someone to say it was common for the ma10 to wear at the front slightly or that .2mm was ridiculously worn out! as frank says .2mm aint much but i just wasnt sure if it was too much to reuse the block. the reason i tread carefully around these issues is that i get so mad when i spend time and money on something only for it to be wrong at the end as im sure everyone does!!! id rather admit defeat and source a new engine! but, if guru ed says its ok, i think i'll buy some rings and rehone bores. one more q tho, am i going for standard rings or o/size filed down? i can't seem to find o/size anywhere. local engine recon place says they can only get standard. also enginestuff.co.uk sells only standard. cheers guys - ne

 

[Ed]

Well I can tell you this my dad had a MA10 engine that had done 250,000 miles with the only thing ever being changed being the pistons rings. It's not the nicest way to do it, but in that case it did work. I have not yet found any MA series engine that has not gone oval.

 

[RTLkyuubi]

#### it lol its only an ma10 engine just drop some new rings in.

 

[nef1000]

ye will do then.new rings it is.cheers.ne