Coil and Piston Ring Recomendations Please

I'm about to start the job of fixing my engine, Does anyone have any good recomendations for replacement coils. The ones fitted are my second set in 2500 miles (is this the norm?), they are after market ones not Yamaha specific.

The other big job I have to do is replace my piston rings. Now, I've never done that before, I'm confident I can do it but how do I tell which replacement rings I need? I see from the parts list that there are about 4 different option for rings and also pistons. At which point (and how can I tell) do you have to replace a piston as well as the rings?

Cheers
Lea

 

Get your self a workshop manual. This will show how to measure the rings, the wear on the pistons and barrels. You are mainly checking for out of round in the barrels and the piston skirts. You will need the tools for measuring, see if you can get the shop to measure the parts for you if you don't have them.

This will let you know if you need new pistons and a rebore of the barrels.

If the parts are within spec you can hone the barrels and reuse the pistons.

The pistons should have a part number and size on them.

You need to clean the piston ring slots and make sure the oil holes in the slots are not blocked and that the slots are within spec (feeler guages).

You will also need to check valve shaft wear and replace the valve seals. Get all the carbon out of the head too.

Good idea to replace cam chain, primary chain and guide while in bits.

Buy or borrow a good torque wrench. Keep everything as clean as possible.

Hope this is some help. Been there done that

 

Cheers Kiwi, I've already done the head, valve stems and seals. I was hoping that was the problem of the low compression but it wasn't . I'll do what you say and take the bits to the local yam dealer to measure for me.
Thanks again.

 

You are welcome, happy to help if I can. If you were a bit more local eh?

Remember to keep the parts labeled as to which barrel they came out of and which way they faced. Don't forget new clips for the piston pins and don't drop them in the motor! If you find you need a rebore new bearings are a good idea. Be careful with the small gasket that goes aound the camshaft hole with the head gasket, here that bit was $90 so I reused it.

Make sure no crud falls into the engine from the barrels where the studs go, get everything as clean as you can first, much packing with rags needed there.

You might as well get the shop to do the hone too cost me $5 so no biggy there.

Good luck.

 

Biggest problem I found was trying to locate replacement rings or pistons. If I remember correctly Yamaha has discontinued the std and 1st over set. I think the 2nd over was available, but was told that some machine shops would charge alot to go from std bore to 2nd over!

 

a good machine shop can check and hone or bore those cylinders out. He can clean the ring grooves on your pistons and even should be able to get rings too.
Be sure he fits the rings to your cylinders for the right ring gap.

If I were to rebuild the whole top end..... I'd replace rod bearings too and depending on the amount of wear on those I might even replace mains.

Good luck there

 

Yep. Damn shame to ruin a new ring job by having a piece of rod go through the cylinder wall.

You've already pulled it down far. Have a looksee at the bearings too.

 

Hi All,

As usual when you start something it just keeps going. I've removed my pistons and they need cleaning, so I'll follow the recommendations you have set out here and elsewhere. However:

A lot of the discussion in this section is over my head. I had hoped getting new rings for the piston wouldn't be overly complicated. Am I best just taking the relevant engine parts to my dealer and getting them to confirm the parts that I need?

I can take some photo's perhaps, but there is a lot of cleaning and a lot of crud in there. It took me 2-3 hours just to separate the cyl head from the body there was sooo much gunk.

Also, I do not have a rotor puller for the alternator or a tool to hold the clutch still while I remove everything as per the manual. Will this stop me from being able to split the cases? Should I just buy this tool?

Thanks as always,
oby

 

If I wasn't clear the first question is really saying should I have a professional look at the pistons to see what can be reused and what needs to be worked on or replaced?

Cheers

 

oby, how'd you make out with this?? I am in the same boat it seems and a bit lost myself ;-)