1988 fz750 (pure sports) head gasket question

[SEMO]

Hello! this is my first post. I recently bought an 1988 fz 750 with 38000 miles on the odometer. I'm not sure the difference in this bike and the FZR. It's a little rough but I figured for my first bike i'd rather have something I don't mind scuffing up . Anyway, it runs great EXCEPT...every 30 miles or so it needs to be filled with coolant. Pushes it all slowly out the overflow tank. I tried a new rad cap and no go. So i've narrowed it down to a small head gasket leak. Well I bought a manual and tore it all apart and I've got the head off but of course the shop sold me the wrong head gasket, its the one that goes between the head and valves...so i'm waiting for the right one to come in. But I'm not sure why the gasket I removed has 3 layers...is this normal? Also, I can still see cross hatching in the cylinders so I'm thinking it may have been rebuilt not too long ago and maybe the head was shaved requiring a thicker head gasket? Anyway my question is, is this normal for the head gasket to have 3 layers or does this mean I'm going to need a special gasket...? heres some pics!

[reelrazor]

That's how they are(OEM gaskets)- laminated metal, riveted together(rivet just to the right of your index finger in picture #3) .

Be sure to clean extremely well in the combustion chambers...look VERY closely for cracks. If there are cracks, they will run from valve seat to valve seat. This was semi-pretty common on these early generation five valve engines......you end up with the exact symptoms you describe.

The gasket you need will be: 2KT-11181-01-00

The crosshatching?? Sheeeit. Unless it looks (feels) very fresh, that's normal for that kind of mileage. People 'break-in' engines waaayyy too easily and NEVER properly seat the rings. That old head gasket looks like it's been there for the duration....unless some jackass went so far as to re-ring it, but didn't spend the $$ on a new head gasket..

[kiki231]

Geez-- what a beautiful bike!
Hey Reelrazor-- can he run any pre- 1988 FZ750 head in that baby? The reason i ask is because there are a lot of old fz's kicking around

[reelrazor]

Kiki,

Yeah,. he can.....problem is that all of them were susceptible to the same cracking. Seems like all it took was one overheating event (one SoCal rush hour trap). The seats can be pulled, the head welded, machined and seat reinstalled.

I forgot to say, he really really ought to backflush his rad, and make sure no bad buildup around the water pump impeller

[SEMO]

Thanks for the replies guys! This is a great forum. Good to know on the head gasket. You're probably right that the engine has never been taken apart although I did have to use an impact screwdriver to get the ruined crankshaft end cover screws out...maybe someone had checked the valve clearance and needed to time it or something. I scrubbed and looked very closely for any cracks in the head. I don't see any but if they're really hard to see then I may have some. Heres some pics of the cylinder heads from left to right. I'll definitely do a backflush on the radiator and check out the water pump. Just put a new rear tire on it a couple weeks ago. Improved the ride immensely.

[reelrazor]

You gotta get that carbon out of the combustion chambers. I suggest Permatex Paint and gasket remover. Spray it on and let sit, use a scotchbrite.

The cracks will be from one valve seat to the other..not out into the gasket surface..


It is usually between one of the exhaust valves and the intake valve next to it-near where the seats siamese. The crack will be small, but will access the coolant passage in the head. This is your 'runs good..BUT uses coolant out the overflow'...It won't show a clean piston like a water jacket to bore head gasket leak..or show white exhaust.

[kiki231]

although you say that bike is "rough", she's a keeper! That is a rare color scheme. It looks stock for the most part, and i would love to be in your shoes.
The heads will need to be cleaned more aggressively (but gently)
If you feel the need to take he valves out, make sure they go back in their correct ports, and DO NOT damage their seats or faces (the points where the valve touches the port surface.
After you clean them you can be sure of their condition. They look ok as they are, but you will know for sure

[SEMO]

Thanks for the replies guys! Feels good to know I'm not the only person that drools over the classic curves of the fz. She's a keeper for sure kiki! I cleaned the areas between the intake and exhaust valves with some steel wool, an old shirt, and engine degreaser and got em pretty shiny. I have good vision and I don't see any hairline cracks so hopefully the head gasket will cure my problem. I did notice that when I took the engine apart the head bolts on the inside weren't near as tight as the 4 accessible from the outside of the engine. Maybe the same guy that stripped the superficial allen screw heads didn't have a torque wrench. Sure didn't feel like breaking loose 27ft/lbs or head bolts I've dealt with in the past anyway (this is my first go around with a motorcycle engine). I've been in and out of gassers, diesels, and 2 stroke jet ski engines of which I've become a shade tree mechanic. Looks like I'll add motorcycles to that list before I'm done here! Glad to be a part of the community!

[SEMO]

Well here's where I'm at. I got my head gasket in and got to checking the valve clearances. All my exhaust valves are right around .20mm of clearance so i'm gonna call them good (.21-.30 is the recommended) but my intake valves (.11-.20mm recommended) are another story...I've got 2 that check out at .13mm, 2 at .08mm, 2 at .06mm, and 6 that are between 0 and .04mm (.04mm is my smallest feeler gauge and it wouldn't even go in 6 of them) I checked all the bike shops in my area and none of them even have pads and they're $13 EACH online. Whats my best option here guys? My shims are between 170 and 185 so I'm gonna need some between 150 and 160 I think. Haven't figured the exact number of shims I need yet. I'm also a little confused on how the clearance can get smaller, it seems to me the clearance would only get bigger. Do the valve seats compress/wear over time?

[kiki231]

HI SEMO
you are good on the shims. As you research, you will see shims go as low as 120. I would spend 60 bucks and buy a hotcams shim kit. They will give you 3 of each size (from 120 to 240, in 5 mil increments). Lots of folks will tell you to buy just the shims you need, but its probably just as cheap to buy a whole kit! If you want to go frugal, buy the shims on-line one at a time. 13 is WAY too high a price-- normally sugg retail is 6 bucks. For my "after-hours " shop, i operate a shim swap deal, -- so no charge, but i keep your old ones. If you want your shims, i charge 6 bucks plus tax. On-line they are anywhere from a dollar to 4 dollars.

If your feeler does not have leafs to go that low, assume the clearance is zero, then remeasure after you put the correct shim in. The logic (which is proven to me by experience) is that once the clearance goes to zero, the wear stops on the valve, and it stops sinking into the head ( and reducing clearance) since the cam prevents it from contacting the seat. The danger with too-tight valves (especially on the exhaust side) is overheating, since contact with the seat allows the valve to dissipate heat. -- not to mention reduced compression and performance.

I am not sure about the 750's , but the 600's are notorious for soft valves that "tulip" into the head. Reelrazor-- is that a prob with the 750's too? Either way, just live with it!

good luck-- you are almost there!!

[kiki231]

oh-- BTW-- Bike bandit is a good source for the shims on line!

[SEMO]

Thanks kiki i think i'll go with the shim kit. Not sure where I got the $13 per shim haha.

[SEMO]

Well I'm looking at the shim kits and they have them in 7.49, 8.9, and 9.49mm OD (Outer Diameter I assume) sizes. I measured mine and they are 6.98mm (.275 in)...am I measuring them incorrectly or will these shims not work on my 88' fz genesis engine?

[kiki231]

ahhhh yes-- the first of the 5 valve heads........
7mm shims -- same as the ducatis

you may have to spend the 8 bucks a shim, or do an exchange with your dealer!

-- the up-side is that they may have them in stock-- so no wait

[McFizzer]

If you take some oven cleaner on those valves with a wire brush and scrub the piss outta it for like 10 minutes you should be in better shape... Just a suggestion, nice FZ.