NC30 cylinder honing/boring

[Neosophist]

Depending on whose riding them I guess.

Properly looked after,

i.e oil changed regularly, valve clearances done and not ran on the back wheel for a long time then the motor is very strong and will easily do over 100,000km barring some really unlucky mehcanical failure, which is again quite rare on a properly serviced motor.

The bikes are 20+ now and lets say an average is 45,000 km.

So if it takes the same amount of time, ie 20 more years then the bike will be 40 years old by the time its worn out from natural causes and you have 20 more years of life in the engine.

To do a full rebuild properly I reckon you could get close to the cost of two decent motors.

Thats 40 years of motoring between the two engines providing they're looked after.

Rebuilding on the cheap often comes back to bite you in the arse.

For example if your motor is suffering from work bores, have you considered the condition of the big end shells too? I bet they will be close if not past their service limit. If your stripping it down enough to do that may as well do the valve
stem seals too.

If your really set on rebuilding the engine then fair enough, but if it explodes and falls to pieces with strange chinese oversize pistons then its a bit of an expensive experiment.

[Maelstrom]

Hi krisztian,
There are two critical engineering tasks when reconditioning a motorcycle engine; the crankshaft journals and the cylinder bores.
1/ In twenty years as a motorcycle mechanic in Aus I found one person who could bore and hone a cylinder correctly. Where exactly do you hope to get yours done?
2/ The torque plate should have a ground finish, so what is the reason for a gasket?
3/ 0.010 - 0.045 is a very tight tolerance and I doubt that the Chinese pistons could run at those tolerances.
4/ I used to use an external mic and dial bore gauge (Mitutoyo) for measuring clearance, taper and ovality. Do you own a set of those instruments? If not who is going to measure to this degree of accuracy and with what?
cheers
Blair

[krisztian_andre]

I won't use the chinese pistons, I'd rather clean and coat the old ones. I've just received this message from the chinese seller:

hello
thank you very much for your visit. i am sorry , i made a mistake , i wrote a wrong title, we don't have the piston kit for vfr400 nc30
very sorry about this.
thank you very much!

Depending on whose riding them I guess.

Properly looked after,

i.e oil changed regularly, valve clearances done and not ran on the back wheel for a long time then the motor is very strong and will easily do over 100,000km barring some really unlucky mehcanical failure, which is again quite rare on a properly serviced motor.

The bikes are 20+ now and lets say an average is 45,000 km.

So if it takes the same amount of time, ie 20 more years then the bike will be 40 years old by the time its worn out from natural causes and you have 20 more years of life in the engine.

To do a full rebuild properly I reckon you could get close to the cost of two decent motors.

Thats 40 years of motoring between the two engines providing they're looked after.

Rebuilding on the cheap often comes back to bite you in the arse.

For example if your motor is suffering from work bores, have you considered the condition of the big end shells too? I bet they will be close if not past their service limit. If your stripping it down enough to do that may as well do the valve
stem seals too.

If your really set on rebuilding the engine then fair enough, but if it explodes and falls to pieces with strange chinese oversize pistons then its a bit of an expensive experiment.

[krisztian_andre]

Hi krisztian,
There are two critical engineering tasks when reconditioning a motorcycle engine; the crankshaft journals and the cylinder bores.
1/ In twenty years as a motorcycle mechanic in Aus I found one person who could bore and hone a cylinder correctly. Where exactly do you hope to get yours done?
2/ The torque plate should have a ground finish, so what is the reason for a gasket?
3/ 0.010 - 0.045 is a very tight tolerance and I doubt that the Chinese pistons could run at those tolerances.
4/ I used to use an external mic and dial bore gauge (Mitutoyo) for measuring clearance, taper and ovality. Do you own a set of those instruments? If not who is going to measure to this degree of accuracy and with what?
cheers
Blair

Hi Blair,

what is there to do with the bottom end? I was thinking of using platigauge to measure the crankshaft journal clearances and then there are different color coded honda journals that I can use.

1 - I don't know. I'm trying to find a place in Thailand if I can. If I can't then I'll send the top case abroad. I think it's possible to temporarily import something without paying duties if it leaves the country within some time.
2 - I read that because of the non-uniform hardness of the gasket the barrel would deform differently without it.
3 - I'm not going to use those.
4 - I had this in mind:
http://www.ebay.com/itm/321110114156?ss ... 1438.l2649
two perpendicular measurments at three different depths.

Are you going to stay in Thailand?

[Maelstrom]

1/ You can already guess my view on that.
2/ Maybe with an Austin A40 head gasket that would be true. Modern motorcycles do not use paper head gaskets.
4/ One hundredth of a millimetre is 4 ten thousandths of an inch. Your margin for error is very small, and it seems that the Chinese dial bore gauge that you refer to does not come with a certificate of accuracy. I can put you in touch with a Thai business who sell Mitutoyo, and I have been very satisfied when doing business with them. pm me if you are interested. You will also need a micrometer to zero the dial gauge and measure your pistons.

If you can get another engine try to get a direct import. You know that most Thais do not change their oil so any engine that comes from a 'local' machine will likely be rubbish.
It appears that I will be here for at least another year or two.
cheers
Blair