XV250 Engine renewal

[fazil]

My first bike was a 1992 year Xv250 bike, i still keep it. It's almost 25 years old but looks very fresh thanks to ebay. I surf ebay for cheap nos parts.
So bike still runs well. But i think of renovating the engine in the future. So i can start to collect the engine parts that i'll need.

For example, i found new cylinders on ebay for a good price (150 Euros)
Can somebody write me, which engine parts will i need for making it new.

 

[TownsendsFJR1300]

It depends on what if anything is wrong with it AND how far do you want to go with it.

If your talking a COMPLETE REBUILD (probably not necessary), your talking ALL transmission bearings, crank bearings (main and rod), cam chain, tensioner, gaskets, seals, etc..

If the gear box is fine a freshen up of the top end (depending on the condition).

**Did you do a leak down test on the engine to check its OVERALL HEALTH?
If it's say 95% tight, your pretty much throwing your money away...

I'd be doing that FIRST, determine if you have any oil burning, etc and go from there..


Side note, my first, 1989 Kawasaki KLR 250, I got 73,000 miles (street) out of the piston/rings(rings were at the end of spec's), original cam chain (3 times longer than the FZ). That engine in particular, liked to have the main left side (rotor) roller CRANK bearing cage fail every 32,000 miles. Part of the cage actually disintegrated (god awe-full noise too!!). At 64,000 miles, it started knocking again. Complete tear down again and replace that bearing.

My 2005 KLR 250, when swapping out the cam chain at 28,000 miles, I checked that same bearing. Sure enough, maybe .005" play. That bearing will need replacing soon...

Sold that and bought the FZ as a replacement..


The main bearing is under that double sprocket gear (cam chain and balancer sprocket):





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[fazil]

I haven't done compression test yet. I'll buy the tools soon. No oil burning. After 3000km of periodic oil change, quantity is the same.

I wrote to Virago Tech forum also and had a reply:


Most air cooled 4 stroke bike motors do not wear the bottom end rod bearings much, so you could probably keep the rebuild to the top end, if you want to buy NOS cylinders and pistons and rings you would then need to rebuild the heads, which would mean taking them to an engine machine shop and having the valve seats and valves ground. A pair of cam chains couldn't hurt either. Use all new gaskets and valve guide seals, position the top two ring gaps 120 degrees apart, on the cylinder thrust side, and torque the heads back on to specs. Use VERY light oil on the rings for assembly, not engine oil and certainly not gear oil, and this will assure a good fast ring lap in.

Rods won't be worn, the big end, bottom bearing is oil pressure fed so is very long lived. Inspect the cam chain tensioners and if very worn put a set of those in too. The machine shop will lightly recut the valve seats and same for the valves, and may resurface the head sealing face, but not normally needed, you can wet and dry sandpaper this on a flat surface easy enough if it looks like it's needed.

ViragoTechForum.com • View topic - Engin renovation (Pistons-Rings-Cylinders etc)

 

[TownsendsFJR1300]

Please look up LEAK DOWN TEST, NOT compression test.

It is very different and will let you know the HEALTH of the engine.

The compression test isn't nearly as effective as a leak down test..
If your engine's leak down % is up above 90%, It DOES NOT need a valve job/top end.

If you look into the exhaust And intake ports IN THE HEAD. you'll see the valve stems.

If there's excessive carbon build up(on either-especially the exhaust) you have leaky valve seals
which would need replacement, perhaps valve guides as well.. Oil passes the worn seals and carbon up
the stems. You would feel a lack of power under load, especially on a 250. I had one (of 2) exhaust valve stem
seals leak as ell as that guide. A big old bugger of carbon built up on the stem and the power was down
EASILY 30%..

Sounds like you want to tear it down no matter what. Even so, you should do the leak down test just
so you don't miss anything that needs addressing.


***BTW, if the cylinder/ piston is worn beyond spec's, as long as over sized pistons and rings are available, a machine shop
(with the new piston and spec's in hand) can punch out yours for a small fraction of new parts.
It'd likely be same place you get a valve job done.....

And just because you R&R the cylinder , it is NOT mandatory to do a valve job (but not a bad idea to have it checked, new
valve seals, etc)


What I use and it's not terribly expensive..





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[fazil]

Thanks Scott,

I don't have any experince about engine insides. So this will be my future (next 10 years) plan to explore what is inside
I'll need that leak test tool and a compressor then.
Can i restore the engine head and valves myself?

 

[TownsendsFJR1300]

Thanks Scott,

I don't have any experince about engine insides. So this will be my future (next 10 years) plan to explore what is inside
I'll need that leak test tool and a compressor then.
Can i restore the engine head and valves myself?

You won't need the compression tester at all..

Removing the valve "keepers" is as simple as smacking the spring just right and it'll come apart and the valve comes out.
Valve seals usually simply slide over a part of the head (inside the spring).

You would need to have the equipment to check valve to valve stem play as well. To re-install the springs, you'll need a spring compressor.

IE, It's much easier to send off the head to a machine shop that re-builds motorcycle heads.
I wouldn't screw with it....

While your that far, pull the cylinder off (I'm assuming it's a separate cylinder, not like the FZ from way back then).
Check piston to cylinder clearances, ring end gaps, etc. If worn beyond tolerances, you'd need to address that.

The machine shop can also check those for you as well(but you need to pull the piston)



**A product that works very well at keeping your top end clean and the fuel system is Yamaha's RingFree.**

I use it in EVERY gas machine I own (including the FZ). It's not cheap but does what it says. It's EXTREMELY
popular in the marine world.

Using it would help starve off carbon deposits, carboned up rings, leaky valves, etc and extend the life of your engine.

Highly recommended...

https://www.shopyamaha.com/product/details/ring-free-plus?b=Search&d=34