Honda NH80 Low compression issues

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yeoruka
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Honda NH80 Low compression issues

Post by yeoruka »

Hi there.

I bought my little nh80 about 6 months back and have been slowly getting it back to a commutable state.
I've replaced fuel lines, reed gasket, cylinder gaskets, piston and rings and exhaust.

This scooter has a history of low compression, I managed to get it up to around 170psi, however a couple of weeks back I was riding down a steep hill ( it takes about 4 minutes to get down ), I don't think I had the throttle open at all and about halfway down I opened up a little which then was followed by a bang and it sounded like it went high revs on a low gear. After that I had low compression again and now it doesn't idle, but it is still running.

I took the engine out to check for damage. Checked the piston, cylinder, gaskets, reed valves etc and it seemed fine. I did a compression test on the cylinder and it came in at around 80psi. I then poured a teaspoon of oil into the cylinder, re-tested and it came out at 180psi. Does this mean I need to replace the head gasket and/or skim the cylinder head (I saw a video of someone using cutting compound on a glass sheet)?

I live in NZ, so getting parts in can be expensive and time consuming so if I can avoid spend $25 to get a head gasket sent over I'd prefer it ha.
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Bear 45/70
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Re: Honda NH80 Low compression issues

Post by Bear 45/70 »

You need at least new rings and a good hone job on the cylinder if you are lucky, otherwise you will need an oversized piston and a cylinder bore and hone job.
Bear 45/70

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