Time for an engine overhaul?

[anjames]

Hey guys,

I got a 2000 GZ250 for _free_ which had been sitting for 3yrs and didn't run when I got it. I'm finishing a PhD in mechanical engineering soon so I figured that working over a motorcycle would be a good test of my skills (or lack of them). Since then I've unsiezed the piston (thanks to Mystery Miracle top cylinder oil), cleaned the entire fuel system including the carb with ethyl alcohol, flushed the brake line, sanded rust off the forks and replaced the fork seals to fix a leak, lubed the chain and replaced the oil regularly. I've never gotten around to adjusting the valves, but it seemed to run fine so I wasn't too worried about them. One of the only problems is that it has a moderate oil leak from the head gaskets (both the upper AND lower ones along the cylinder) which over time covers the case in oil and requires occasional cleanup and topoff. The bike and I have gotten along nicely for the most part, and I've happily driven it to work the 5mi along the coast almost every day since getting it running (maybe 6mos).

Yesterday on my way home on the freeway I'm pretty sure I blew the rings. I don't typically ride on the freeway, but I have some friends who I brew with on the occasional Saturday and they live about 20mi down the freeway, so who knows if it was the freeway driving (at speed 65mph), or if the rings were just ready to go and I was unfortunately on the freeway. I had a sudden (brief) loss of power and after that the bike started blowing LOTS of blue smoke (ie burning oil) and revving uncontrollably when not in gear (but not delivering a huge amount of power when in gear). There is also some oil collecting at the end of the tailpipe. When cold it will run ok (with smoke) and not overrev, but as soon as it warms up it just revs through the roof and I have to modulate the kill switch to keep it from blowing up at stop lights. I can only guess that the overrev is due to the oil getting past the piston, vaporizing when the engine is warm, and detonating so that even though the carb isn't putting much gas in, the oil burning is enough to rev the motor up? Anyway while I was able to get it home, it's obviously not a safe ride in this condition, so since I got the bike for _free_ and I'll have some time on my hands while finishing my thesis, I'm planning to take the top end apart to replace the rings and head gaskets which should keep me busy for a while.

So my question to those of you with experience in these things is: are there any hitches I should foresee in this job? Are there any magic tricks to getting the head apart and back together without too much grief?

There is a 'special tool' listed in the service manual for adjusting the valves, which I'm pretty sure is some combination of a hex wrench and a square wrench, but I don't know where to get one. Any tips on adjusting the valves?

Also, since the head gaskets and the rings failed, these are obviously weak links in this otherwise reliable motor. I would be very happy to replace these bits with the best quality parts around, so are there more robust replacement parts in the aftermarket than the OEM ones?

I noticed that the bolts attaching the pipes to the head are pretty rusted, so I'll probably order a new set of those as well just for good measure, but I've heard that these can break off if they're too badly rusted, in which case it's enormously difficult to remove the broken off ends and the motor might be considered a bust (though I could probably drill them out and re-tap the holes if necessary). Any tips for getting these out in one piece?

Also, should I bother cleaning out the pipes beyond just draining any remaining oil out of them?

Thanks! Alex

[5th_bike]

The Kawasaki valve tool kit mentioned in this thread seems to work better than the original Suzuki OEM kit:
http://www.gz250bike.com/forum/viewt...ve+tool#p35656

I found one by Googleing the part number Kawasaki 28-1972, and bought it. It works great, indeed.

I never took the head off, so, the best of luck with that !

[blaine]

If you can get the exhaust bolts out of the head,replace them with studs.That way you never need worry about them galling the threads.Should always be studs in aluminum when possible,a factory mastake IMO. A Schrader valve or a Robinson head screw fits the valve adjuster perfectly. :cool:

[geezer]

good luck cleanin the pipe, i wouldnt know of a good way to do that other than just run the bike till it disappears again :techy: i wonder why it doesnt blow smoke cold, might be worth testing compression maybe. have you checked the spark plug for oil?

[anjames]

@5th_bike: I googled after that part (which looks like it would sure do the job) and found only the denniskirk retailer which lists this product as 'no longer available', and I couldn't find it at several other online retailers. Also couldn't find the OEM Suzuki kit you mentioned, got a part number or a link? I guess I'll keep looking around in the meantime until I find something, or just go for the Robinson head screw if I can get a socket wrench in there.

@blaine: I sprayed down the bolts with some WD-40 and will let it sit for a while before giving them a shot. Plenty of rust flaked off 30 minutes later when I gave it a go with my wrench, but none of the bolts galled at all so I'm pretty happy with that bit. I guess stainless studs would be a good option for replacement since they won't rust so much?

@geezer: It still blows plenty of smoke even when cold, and yes: the spark plug is covered in oil. I will probably just drain whatever is left in the pipes, then just run it and let the remaining oil burn out of the pipes, or maybe use some ethyl alcohol or gas to try washing out most of the oil. No point in scrubbing them clean at any rate, except I might take some steel wool to the exterior rust while I've got them off ;-)

One new complication is that the fuel valve was leaking substantially (in the on or reserve positions, full flow in the prime position) after I disconnected the three tubes attached to the gas tank. Maybe that is why the motor was overrevving? I'll take it off and look it over to see if I can fix it, since freaking $85 for a new fuel cock assembly is more than all my other parts put together so far! WTF?! Anybody have experience with this sort of thing happening before?

So far I dug up the following parts list:
11141-38201 GASKET,CYLINDER 1@$22.34 $22.34 (upper)
11241-38301 GASKET,CYLINDER 1@$5.46 $5.46 (lower)
14181-37D00 GASKET,EXHAUST 2@$3.16 $6.32
09103-06203 BOLT,EXHAUST 4@$1.78 $7.12
12140-49270 RING SET,PISTON 1@$30.79 $30.79
Subtotal $72.03

I think I will have it all apart before I order though so I can make sure there aren't any other things I need to put it back together again.

[blaine]

Originally Posted by anjames

Also couldn't find the OEM Suzuki kit you mentioned, got a part number or a link? I guess I'll keep looking around in the meantime until I find something, or just go for the Robinson head screw if I can get a socket wrench in there.

@blaine: I sprayed down the bolts with some WD-40 and will let it sit for a while before giving them a shot. Plenty of rust flaked off 30 minutes later when I gave it a go with my wrench, but none of the bolts galled at all so I'm pretty happy with that bit. I guess stainless studs would be a good option for replacement since they won't rust so much?

The part number for the valve adjuster is 09917-14920.I have one,and only used it once,as I found it too long for adjusting the intake valves,I found that a schrader valve worked much better.

When I installed my studs (stainless) I put red loctite on them so that they were permanently in place.
:cool:

[anjames]

Well blerg. I took the fuel cock off and there is a small scratch between the prime and reserve positions which is causing a leak from the tank through the reserve, to the prime. From what I could find online, you can only purchase whole fuel cock assemblies, not the separate gaskets. It's essentially just a flat gasket though, so I bought some 1/32" Viton 6"x6" gasket for $6 from McMaster and will just cut a new one out of that. McMaster to the rescue!

@blaine: Thanks for the part number for the wrench. I found it one one online retailer and it looks like this ($30!) tool isn't a co-axial hex/tappet combo like the Kawaksaki's, so I guess I see why people opt for a Robinson head screw instead. Maybe I'll check at my local shop to see if they have any of the Kawi tools.

[anjames]

Apparently the thing to google for this tool is 'tappet tool' and there are like a million different retailers selling kits with an 8, 9, and 10mm wrench with both 3mm (ie for GZ250) and 4mm square pieces. Also, it looks like the Kawasaki part 'SS20' from above has been superseded by 'SS49' which is listed at several places on google.

EDIT: SS-49 is for metric Triumph bikes, and doesn't work for GZ250's. Get yourself a Motion Pro P523 set instead.

[blaine]

Originally Posted by anjames

@blaine: Thanks for the part number for the wrench. I found it one one online retailer and it looks like this ($30!) tool isn't a co-axial hex/tappet combo like the Kawaksaki's, so I guess I see why people opt for a Robinson head screw instead. Maybe I'll check at my local shop to see if they have any of the Kawi tools.

If you are going to use a Robinson screw,just put a small length of vacuum hose on the screw,so it can't fall into the engine.
:cool:

[5th_bike]

Originally Posted by anjames

I googled after that part (which looks like it would sure do the job) and found only the denniskirk retailer which lists this product as 'no longer available'

That seems to be the case indeed. I checked at Dennis Stubblefield (the manufacturer of the toolkit "Tool #20") and they no longer make that set. However they do produce a universal 6-piece set called "Tool #55" which is available online. I'm quite sure one of those will fit. Too bad though - the "Tool 20" kit already consists of 4 pieces, two of which I will never use.