Engine problem - 660 conversion?

[trifgeorge]

Hi guys,
My bike burns oil (about 600 ml/1000kms). I also did a compression test with these results: cylinder1 - 90 psi, cylinder2 - 90 psi, cylinder3 - 85 psi, cylinder4 - 110 psi. My question is: Will 4JH cylinders and pistons fit my 3he?

[racerd14666]

if i remember correctly the 4jh is basically a yzf witch yes will bolt up but the piston pin bore is different but il let some one els confirm that cus im not 100% on that,

[trifgeorge]

Thanks for response.
what i wanted to do is use the 4jh cylinders and pistons and still use the 3he cylinders head.

[trifgeorge]

anyone else ??

[cad600]

Yep, the 4JH pistons and rods will work with the FZR crank. You really need the 4JH piston case as well to make it easier. The FZR600 valve head will bolt up and should work. But the YZF600 valve head will be more efficient as you are basically building a 660 engine. You will also need a 3mm spacer to raise the valve head up because of the additional crank stroke.

Side note, are you doing this to avoid having to use the 4JH piston sleeves and head? If so, I don't see why you can't use the FZR stuff and have it bored out for the pistons. But you will need to find a shop to do the bore and I think the sleeves will need to be plated. This process is usually very expensive and will not usually offset the cost of using the YZF600 items. Price of course depends on what you can find near you and if yo trust the shop doing the work.

[trifgeorge]

CAD, as I said in my first post, the bike eats a lot of oil and has low compression on all pistons. I don''t want to replace my engine with another one from a FZR 3HE as they are all known to burn a lot of oil. But i can't afford to buy a complete YZF engine as they are quite expensive. So what I'm trying to do is fix my engine without spending a ton of money. I found a cheap set of pistons with rods and cylinders to match them from an 4JH on ebay for about $160.

No, I don't want to avoid using the piston sleeves (cylinders) of the 4JH. I want to avoid using the head of the 4JH as the one that i have on my fzr is in good shape. I agree with you that I could use the 4JH pistons and rebore the FZR cylinders to their specs and then replate the cylinders, but as you know that is pretty expensive.

So this is what I have in my mind:

- throw away the FZR pistons and cylinders
- bore the FZR rods so they can accept the pin from the 4JH pistons (this will avoid the need to make a 3 mm spacer and,if i'm not wrong, having to buy adjustable cam sprockets as well)
- mount the 4JH pistons on the FZR rods
- mount the 4JH cylinders
- mount the FZR head
- mount the FZR carbs
- TAKE IT FOR A SPIN

Am I missing something in my transformation process?

P.S. What cylinder block gasket and cylinder head gasket should I use on this swap? The 3HE ones or the 4JH ones?
P.P.S. What do you think about head porting?

[trifgeorge]

Anyone??

[Freestyle72]

Yes you can bore the FZR wrist pins, but they are known to be weak, boring them out won't really help the situation at all. It seems like you need your bike as a daily rider. Most guys wouldn't want to have a grenade like that as a daily driver. Especially since the 660 has a lot more compression and torque, so you are basically going to stress out a piece that was designed for 85whp, and then cut it down some, and put like 100 or 105whp on it...

[trifgeorge]

I understand.Thank you Freestyle! I'll use the YZF rods then. What I really want to know is if I can use the 3HE cylinder head instead of the YZF one. That would save a lot of money not only because I would not have to buy an YZF head but I would not have to buy the carbs either.

[Freestyle72]

since you are in europe it might be easier for you to get your hands on the FZS600 rod which has the same wrist pin diameter as the YZF but is the same length as the FZR600 rod. So no spacer plate, or adjustable cam sprockets...and apperently the part is lighter than both the FZR part and YZF part.

But I would still try to find the YZF head to make life easier and you will have a better engine.

[trifgeorge]

I found some rods from a 2000 FZS 600 for about $140.
Acording to THIShttp://www.fzrarchives.com/fzr400/560.html web page, the YZF head will bolt straight on to the FZR cylinder block with no problems if the FZR cylinder block has at least 1mm overbore so the valves can clear the cylinder wall when they open. That means that the FZR head will bolt to the YZF cylinder block without problems.

All I need to do is figure out the rods problem. I would really like to see some input from someone that has actualy bored the FZR rods and had (or not) problems with this mod.

[Freestyle72]

How much will it actually cost you to have your cylinders bored to the accuracy required vs just looking out for a good deal on the rods?
http://www.ebay.co.uk/itm/Yamaha-FZS600 ... 4cf89cab14

4 rods cheaper than $140... dunno what shipping will be

[trifgeorge]

the price on those rods and shaft should be around $120 including shipping. I don't know how much it would cost to bore the cylinders and recoat them, but new pistons+ rings should be well over $600.
By doing the 660 mod the cost are:
YZF cylinder block and pistons $140
FZS rods $120
Cylinder block gasket $19
Head gasket $38
Valve seals $51

[Freestyle72]

whoops my bad... I meant have your rod ends bored.

[Freestyle72]

the price on those rods and shaft should be around $120 including shipping. I don't know how much it would cost to bore the cylinders and recoat them, but new pistons+ rings should be well over $600.
By doing the 660 mod the cost are:
YZF cylinder block and pistons $140
FZS rods $120
Cylinder block gasket $19
Head gasket $38
Valve seals $51

http://www.ebay.co.uk/itm/YAMAHA-YZF600 ... 3f0f659739
Cylinder block and pistons for $75ish

http://www.ebay.co.uk/itm/Yamaha-99-YZF ... 53e911cbef
even cheaper...