How hard to install big bore...

[Crazcnuk]

How hard would it be to do the big bore kit while the engine is in the bike?

I have the whole top end off, right now, and found a big bore set of barrels, pistons and rings already to go, just need to install.

Are the piston pins full floating, or do you have to take the rods out to press them in?

Do any modifications have to be made to the cylinder head?

[trbig]

If I was going ahead with the bore, I would get the valve guides and seals along with a valve seating done, and new piston pins. They are not pressed in. Remove one of the circlips that are on either side of the piston pin and push out that same side. They may need a little coaxing, but nothing drastic. Good luck.
Others know much more about this, and there are many things you COULD do, and a good machine shop bores the cylinders to each piston to be used, but no.. the big bore doesn't necessarilly affect anything below what you have apart if everything in the cases appears good.

Tod

[Ken Talbot]

The piston pins are full floating, you can get them out by carefully driving them out with a small hammer against a piece of wooden dowel. I did a top end job on Tsunami a while back with the block still in the frame.

I'll add that I did that rebuild out in my carport in January/February, and while it may not have been as cold as it might get for you in Hinton, it was still not a very pleasant experience some nights. When I finally getting around to installing the big bore kit I've got sitting in thebasement right now, I'll pack the block into the basement where it wilol be warm and well-lit.

[Pat Kelly]

I have all the parts ready for my big-bore kit (just need $ to have the spare cylinders bored). I will probably do it in the frame. I wanted to remove the engine and detail everything but that will wait till a different winter.

[Crazcnuk]

What I've got a line on, is a set of pistons, with the barrels already fitted together, complete with rings etc.

They are used, but so little, you can hardly tell the bike was run. It looks like the PO redid the engine, and then ran the bike into a wall.

The cylinder head is gone, but I already have mine in being redone anyway. I was going to have to buy 4 sets of rings to finish the job I already started. I can get entire setup for $200.

Wasn't considering a big bore, but this sounds pretty good at the point I am at now.

[Crazcnuk]

BTW, I have the bike apart in a Canadian miltary ammo tent in my back yard!

[TADracer]

If you have access to the parts before you pay for them then I would suggest you have the pistons and cylinders miked for tolerance.....just to make sure.

I am sure others here would know what the measurements should be cause I dont. It would be a shame to lay out the $$$ and find that everything is wrong.

[trbig]

According to the Yamaha book, you subtract the diam. of the piston from the diam. of the cylinder. Standard clearance is .050~.055mm (.0020~.0022") and the limit is 1mm (.0039")

It says to take the MINIMUM cylinder measurement and subtract the MAXIMUM piston measurement.

Tod

[TopCatGr58]

Hey Crazcnuk,

Great find! Just make sure you keep the pistons matched to the cylinders they are currently in!! The cylinders should have been match bored for their respective piston. Take a marker and write on the top of the pistons their #'s, 1, 2, 3, 4!

I did my big bore out of the frame, but did not split the cases, just put rebored jugs back on after mounting pistons. You'll want to do the inner 2 first, 2-3, and then the outer two 1-4 due to how they present when the crank is turned. Put the wrist pin keeper in place on the inner side of the pistons, you'll be able to reach the outer ones easier!

Hopefully the bottom of the new jugs are tapered on the inside? I slathered the cyinders and pistons and rings very well with oil, and then fitted the jugs down onto 2-3 first, compressing the rings with just my fingers, and had the head slightly tilted, once I got those two pistons in, then I rotated the crank to raise 1-4 and lower the head down to meet them, and again pressed the rings and was able to slide the remaining pistons into the jugs, and then slide the jugs down onto/into the case! Then the head and cams, etc.! Good Luck!
T.C.

[andreashweiss]

The bigger pistons and jugs are some I am selling. The motor cranked over nice before I took it apart. Did not know it had the big bore until I had already sold the head. I put each piston back in the proper hole, after taking them off the connecting rods. Neat feature was the wrist pin was held in place by two small alum caps that slide onto each side of wrist pin. Really nice stuff. Remember the price I quoted included shipping only in continental USA not Canada. andreas

[Crazcnuk]

Heh, well, I'm in Alberta, Canada, so that will be extra.

I really hadn't considered doing anything other than fixing the valves I bent, and reringing the cylinders, but those parts are intriguing...

[mro]

Big bore

Machine work on your jugs usally $120/160.00
pistons $300/400.00

If I had the cash would go for it.
Would be cool to have two 1200 XS'es


mro

[79XS11F]

In my opinion the engine is so easy to re & re in these bikes that I would do this sort of work on the bench.
I have run my newly big bored engine for just under 500 Km and it is just starting to "loosen" up and perform well. It's worth the time and effort to do.
Rob

[Crazcnuk]

What am I going to need in the way of Carb mods or anyother mods?

I won't know the exact bore out until I measure them, but looks like:

1196cc
4 into 2 SS exhuast
1980G
Stock airbox at the moment (although I can change this, was looking at the K&N oval filters that go on two carbs.)