nx650 dommie rebore?

**gozell** · #1 8 Jul 2003

Just came down from Europe to Namibie on my dommie and it appears the bike is quite shafted.

After replacing the timing chain it went for 20km and then broke down again. sigh, no compression! The whole thing has now been taken apart and needs a rebore/valves grinding after 50.000kms...

According to the mechanic its because of dirty/old/mixing oil etc which is far enough.

What im wondering about is, if i do go for a rebore -to be honest not much choice- what other damage is possible awaiting to appear inside the crankcase?

Is there anything to be said about the reliability after a rebore?

Any ideas/other tips?

**rob46** · #2 10 Jul 2003

Hmm - I'm not sure about the rebores as i've never had one done.

Depending on how much this lot could end up costing, it might be easier to try and source a second-hand engine.

That however might not be an option depending on your location.

Good luck anyway.

**jim stanley** · #3 21 Aug 2003

I sucked in much dust in northern Bolivia and had to do rebore in LaPaz. They put a new sleeve in with standard size piston/rings. Would have gone big bore, but the only piston in Bolivia was standard size. Total cost was about US$320 (cheap labor in SA). It was pretty straightforward.
I didnt replace the valve guides like I should have because I didn't want to open that can of worms too. It runs great and strong, but smokes on startup, due to dust-worn guides.

**jim stanley** · #4 21 Aug 2003

one more thing- mine was a XR650L, not dommie, but same engine, I'm told.

**Steve Pickford** · #5 21 Aug 2003

An accurately re-bored cylinder should give no problems, especially if a genuine piston is used and the cylinder is machined to the specified clearance. The last thing you want is a cylinder bored to the wrong tolerances or bored at an angle. This will place a lot of load on the crank and con rod (I've actually seen such a cylinder). On some small single cylinders it's possible to have them bored out on a lathe but I think the Dommie may be a bit big for this. I may be wrong but I think that a lot of aftermarket piston kits result in a higher compression - can result in a hotter running engine and detonation if using low quality fuel also. If you an aftermarket piston, compare the height of the respective crowns, you'll be able to judge if the compression will be higher. This can be overcome to a certain extent with an extra base gasket.

Lapping the valves in is no big chore if you have the right equipment. Remember to ensure that all grinding paste is removed and everything cleaned out afterwards. If not, you'll soon need another engine.

Godd Luck

Steve

**gozell** · #6 28 Aug 2003

the whole thing cost me about 500 euro's (labour only, excluding parts) and its still going after 10.000km and not using oil... im the meantime im sticking vigouriously (?) to my oil change interval....

just too bad my DID520VM chain snapped today, but hey you can have everything.....