Was ONLY going to replace a blown head gasket on my LOVELY 1VJ today- planned on having the whole job done during my lunch hour - but on inspection found that cylinder probably needs reboring. (On account of the shiny bits inside being a bit wavey, instead of straight, which probably caused the leak in the first place.)

Q1: Can anyone recommend engineers (is that what they are called?) in or around London or the Southeast?

(No thank you Bolla - not the guys who did your engine please. I really am hoping to have it all back before the end of the year, without having to remortgage )


Q2: ALSO -- if the hole is bigger, does that mean I need bigger rings?

Where do I buy these? What are they called? Will the engineer shop tell me what I need?

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You need to find a good machine shop. You may need to bore the cylinder to the next size piston if the scoring is deep or you may only need to hone it if it's not too bad. You still probably should get a new piston and rings and while you're in there replace them.

Don't go to any machine shop you find, look around and ask first. Call local dealers and motorcycle shops and ask them if they can recommend you anybody in the area that knows how to get it done right.

If he's still around, I can recommend Brian Parsons Engineering

Church Crookham, Hampshire

01252 615451

He's done three or four rebores for me over the years and he used to supply piston, ring, gasket kits.

There are a few way to go about this and it all depends on how bad your cylinder is...

You might just get away with honing the bore if its just shiny in places. You need to measure the bore in a few different places to see how bad it is so don't go crazy just yet.

Yamaha sell piston rings for difference stages of overbore. Your dealer should be able to give you the specs for the rings.

What was the mileage ? Were you blowing oil before ???

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Hi Mardi
These people in Sutton have a pretty good reputation, although you may well find somone closer to you in London. Sutton Rebore Service Ltd Sutton, 36 Lind Road Sutton - Engine Rebuilding & Reconditioning

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'He who laughs last, was too slow to get the joke'

Pyreknees-up team, Adventure team 668

Just got my xt6's rehoned barrel done by these guys from personal recommendation - 12.5GBP+vat. Just used a new set of std rings as it wasn't a rebore. Planning on a rebuild of it all this weekend.

Quote:

Originally Posted by tedmagnum There are a few way to go about this and it all depends on how bad your cylinder is... You might just get away with honing the bore if its just shiny in places. You need to measure the bore in a few different places to see how bad it is so don't go crazy just yet. Yamaha sell piston rings for difference stages of overbore. Your dealer should be able to give you the specs for the rings. What was the mileage ? Were you blowing oil before ???

Only done about 500 miles since buying it - so problems were possibly inherited. Ran okay until head gasket went.

Used a digital caliper to measure round the cylinder and the difference is max 0.08mm. Not sure if thats critical?

Anyway - cylinder seems least of my problems.

Ground the valves just now (wow! didn't know one can have so much fun twirling sticks!), and discovered that both exhaust valve seatings are pretty crappy (very unevenly worn) which I'm told will need reseating?

I guess best thing is just to take the head and cylinder to a machine shop to have both checked out and fixed.


PLUS one of the inlet valves wouldn't come out smoothly... it gets stuck- seems like the valve stem is bent. (Cos I tried the other valve in the same hole, and it slid in and out easily)

Soooooo.. I'm going to cry for a little bit. Have some wine. And then tomorrow think about what to do next. (Have my hair done, I'm thinking).


If anyone has a spare valve floating about...

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With that discrepency, I would just hone the cylinder and if the cylinder is within standard spec, a new set of standard rings (about £25). Its probably just glaze on the bore.

You can hone your own cylinder if you have a powerdrill and a DIY hone but paying someone £12.50 is even better value, especially if you haven't done it before.

Cylinder Hone Set 4-in1 Sealey VS029

A test to see if your valve is seating is to reinstall them then pour WD40 into the exhaust and inlet ports and see if it dribbles out at all (best leave it 20 mins or so)..

I take it when you ground your valves you used 2-3 different grades of grinding paste ??? You should get them to seat properly with twiddling sticks.

As for the valves, some are easier to get in and out that others. Doesnt necessarily mean they're bent although its not hard to check with a straight edge. Maybe they just need decarbonised with some VERY FINE wet n' dry paper. As long as they slide easily when installed, it "should" be ok.


But... if you can't be arsed with it all (and who could blame you), getting a machine shop to clean your bore and seat your valves (with NEW SEALS) shouldnt be too expensive. £100 maybe.

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See my post and link about bike engineering in London. -ABE .

Can't find it... link?

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