Welding on head? 77-78 vs 79 heads w/extra bolt by cam tunnel

[Chuck78]

Today I picked up my 79 GS850 cylinders and 77-78 GS750 head from the machine shop for a performance valve job, and I realized an oversight that I made before... 77-78 bikes were prone to weeping oil at the front of the cam chain tunnel, and in 79, the heads and cylinders protruded a bit further forward and had an extra bolt there to keep this area clamped, as it is far from the head/block studs.

In this picture, I have the 79 GS850 block with the extra bolt boss stacked on top of the head that I just had the machine work done to. I was thinking of how I could clamp this area, and came up with some ideas. I cannot move the bolt inwards any further as it will be right into the cam chain tunnel o-ring area then. Looking at it from the angle in this photo that I snapped, I was thinking that since half of the bolt hole in the block was covered by the head, I could still use it to get some clamping force onto that area. Then I looked at this broken KZ650 cam chain tensioner that I just tossed in the scrap pile, and instantly thought of using the aluminum to make a piece with a step cut and a threaded hole that will sit on this flange of the head, and just clamp it down.

Then I thought maybe I could do that and mill it down at the right angles to fit snugly against the cam chain tunnel, clamp it, and weld it with my MIG spool gun to the tunnel area. Too bad I didn't see this before I had the head milled, as I will not go anywhere near that nice fresh head surface with the welder...



In my past experiences with welding cast aluminum, it proved quite tricky, but I do have a trashed head in the seized engine to practice on. What's the verdict? I may chop up this KZ aluminum piece into the rough shape and fit it up for a better photo.

[Chuck78]

[Nessism]

I wouldn't worry about it.

[Chuck78]

My '77 engine has been leaking for years & years there, & the seized '78 engine that has been parked in a barn &not ran since 1986 has TONS of oil & grime below that area on the front of the block (worse than my running '77). There was a major reason Suzuki added that extra little bolt in '79. And here I was yesterday looking at the parts fiches, scratching my head as to why the 79 model took a different head gasket part number than the 77 and 78! I had forgotten about this improvement on the 79 heads.

I suppose on 77-78 models still using the 750 head gasket and cam tunnnel o-ring, you would just want to apply a liberal amounts of Threebond 1211 on the cam chain tunnel o-ring in that area to make up for it, as I noticed the white silicone 1211 residue on this head when dismantling. I am using the 73mm bore GS1100G head gasket that is now the standard superceded replacement for the 8 valve GS850, 1000, and 1100G shaft drive engines. It is a multi-layer steel gasket and no longer requires use of the cam chain o-ring, so I think this will be more critical in my application especially. I could run the $36 head gasket z1 sells with the 72 mm bore, same as my MTC 72mm pistons, but the MLS gasket is much stronger...

I think I will have a go at chopping up this Kawasaki aluminum scrap and practice welding on this trashed corroded ruined 78 head, and at the very least I will drill the edge of the 78 head that I am using and just use the piece as a threaded clamp. everything I have done preparing for this engine build, I keep telling myself - do it the best way possible, all OEM, best parts of two engines, tolerances checked thoroughly EVERYWHERE - I DO NOT want to have to pull this head off or split the cases anytime soon!

I suppose the ultimate call will be once I start welding on the junk head, see how the alloy actually takes to welding.too bad I didn't catch this before I sent the head to the machine shop, I could have welded it fully on there before they decked the head, then it would have been totally unnoticeable. at this stage, I will just be welding it to the cam chain tunnel area, and not the flange that projects out that is the other side of the head gasket mating surface at the very front.

[blowerbike]

that 6mm bolt torks around 90 inch pounds....think about it...

[Nessism]

You're gonna F up your head if you go welding on the stink'n thing. Warp it or something. Looks like it was surfaced and everything. Beautiful. Just slam the engine together and take care to torque the head at regular intervals - every valve adjustment should assure a good seal.

[rustybronco]

If you're that worried about the extra clamping force from an additional bolt, make a metal block that will catch the head, drill and tap it and run a bolt up from the bottom side.

Problem solved- no welding required. (although you might have to grind away a slight amount on the head so the bolt will clear)

[Chuck78]

If you're that worried about the extra clamping force from an additional bolt, make a metal block that will catch the head, drill and tap it and run a bolt up from the bottom side.

Problem solved- no welding required. (although you might have to grind away a slight half of amount on the head so the bolt will clear)

yes, that was my initial plan, throwing some tack/stitch welds onto it were an afterthought. Yes, I was worried about warping the head, and that is why I said that if I was going to weld it, it would not be anywhere near the gasket surface, just on the cam chain tunnel, which is quite rigid...

Yes, I would have to remove a little material from the head if I were to make just a clamping block, half of the hole in the cylinder block is obstructed by the edge of the material on the head at the front of the cam chain tunnel. I will try this out, as this leak issue seems to be a recurring problem on many of the older models. thanks for the advice..

[WShie]

If you're that worried about the extra clamping force from an additional bolt, make a metal block that will catch the head, drill and tap it and run a bolt up from the bottom side.

Problem solved- no welding required. (although you might have to grind away a slight amount on the head so the bolt will clear)

+1
Good idea,
Make an aluminum c clamp to cinch it down and leave it at that. all welding will do is distort your clampimg surface making more prone to leakage

[Chuck78]

Well I wasn't 100% happy with my head anyway after the machine shop de-carboned the combustion chambers to expose a bit of pitting in the aluminum in a few places, so that and everyone's cautious words prompted me to find two other 79 heads. the first I found local, but was black with soot from a carb fire, too much work to clean up, so I found a nice second head for $64 at a a bike salvage yard a few hours north, where I just happened to be at this weekend for a wedding... Nice shape, cleaning it up tonight and taking it and a GS650 top end to the machine shop for valve jobs and honing the 650 cylinders... Funny thing is - this 79 head never had the hole drilled and tapped! I noticed it on their ebay listing, but thought maybe it just didnt go all the way through. I got it in my hands and realized that hole was never even drilled into the material that was there for it... Drill and tap time now. I can rest assured that I will not have the pesky oil seepage problem now on my ultimate GS750 buildup...