Day One - New Project

[bobwhitman]

Max-

I thought the 93 v 94 were different exhaust diameters (?) Also, I'm pretty sure you'd have to do some significant "adjusting" to get an HT3 pipe on an early frame. They were designed for 97 and up frames.
Bob
PS- Others (Paul? Ed?) can confirm, but I'm pretty sure Harry used JB to fill in cylinders, so why wouldn't it work on the head surface?

[mac]

I was talking with Alex Snoop yesterday about a questionable sealing surface for a crankshaft seal on my Ossa 175.He said to use a product he has been using for thirty years called Devcon two part epoxy around the seal.He use to do a lot of flat track racing and ran stuffed crank flywheels which would cause enough pressure to blow crank seals out.He would cement the cork in the flywheels and the crank seals with Devcon epoxy and said he has a crankshaft thats thirty years old with the cork still inplace.
I,m thinking it might work,if nothing else,to glue your head gasket down or to maybe just repair the surface like you would with JB.

Good luck and keep the pics coming! Mac

[BrianZ]

For what it's worth, I would have the cylinder milled to restore the sealing surface. After it is milled you have two options, the first being to double up on head gaskets, and the third being to re-machine the combustion chamber. Before (and after) machining the combustion chamber be sure to check the squish band depth using the tried and true solder method.

As for JB Weld (and any other epoxies), I am sure it works fine for intake tracts where it is cooled by the incoming intake charge, but I would hesitate to use it where it is exposed to high temperatures and pressures. That's not to say that it wouldn't work (it just might), but I would be worried about it failing and creating a leak, with the result being a lean condition.

Brian

[Zyx]

Devcon is another manufacturer, or at least retailer, for epoxy. We used to use Devcon back in the 70's because there were few others. These days, lots to choose from. As long as you use 24 hour stuff, it is all similar. I would rate Devcon and JB about the same in application. Don't know what they are rated for in strength. Pretty sure my 93 cases have Devcon in the crank case for stuffing.

As far as using it to resurface the head seal area, if you want to try it, try it. Not much to lose. It it doesn't work you can still grind or burn it out and weld it. It just wouldn't be my first choice. But then I have both MIG and gas available in the garage. Get it clean and abrasive blast it first before epoxy. I think it would resist the temperatures the gasket would see.

Braze might work, just as JB might work. Braze is the more likely candidate because properly fluxed will have a better grip on a shallow pit like yours, and can be machined. As in once in there it won't come out. Get it clean first. Warm it gradually over a greater area than the repair and flux it and braze it, then keep it warm while it cools below the melt point. Maybe it makes no difference but cast iron doesn't like rapid heat and cool cycles. Yours is a non structural repair. Give it a try. I would do braze before epoxy. Then get it flat with a sheet of w/d on a glass surface for a final flat finish. If that fails get it professionally welded and remilled. If you have to weld over braze it will have to be ground out to remove the brass. Braze really interferes with arc welding.

[hodakamax]

Hey everybody! I've arrived home from an evening of dining out and am overwhelmed by a wealth of information! I guess that's what the forum is all about. First, thanks Bob, for the pipe info, just thinking, I have both 93 and 94 cylinders here, I'll measure the exhaust diameters tomorrow and get this figured out. Mac, Brian and AZ, thanks for your input on patching the cylinder. I do have an excellent machinist in town that's gotten me out of several messes. I think I'll take it to him and have it done right with welding and machining. He's quite capable. I'm starting to be spooked on epoxy in an area with both high heat and pressure. I"ll keep you posted on progress.

Thanks again gang!

Max

[hodakamax]

OK, I'm lost. What did this exhaust nut come off of? It fits a 92/93 cylinder and I thought it came from my 94A but didn't.
Thanks!

Max

[hodakamax]

Hmmm---- the mystery deepens, It seems my old short tracker has the same nut. It's on a 92 cylinder. I'm beginning to think this might not be a Hodaka item. Maybe my old pipe fabricator from decades ago used something different to convert it to a slip fit. Any other ideas?

Maxie

PS--Another thought. Is it possible that this could be from the 91 series of "R" parts?

[bobwhitman]

Max-
A slip-fit "receiver" that fits a 92/93 cylinder should (I believe) be off a 96 (chrome Squirt). They used a slip-fit pipe. A 94 used a "screw-on" pipe, whereas a 94A used the slip-fit.
Bob

[hodakamax]

Thanks Bob, the one on the flat tracker was way before Dirt Squirts. The 01 Squirt bolts to the cylinder and the chrome tank shows a 902508 screw-on ring. I'm starting to think these are from the late 1960s and something that I ordered from Hodaka to make your own pipe. It's all one piece and about 1 7/8 inches long. I think you're right on 94s being larger than the 92/93 exhaust diameter but I still can't find a 94 to measure. I back-tracked myself and the one shown in the picture (with the exhaust tool) came off a race engine out of my shop in that period. A mystery indeed. Where's Clarence when you need him?

Maxie

[Zyx]

Max,

Welding is best way to go. My concern with epoxy is that it essentially lays on top of the metal. There is some interaction at the junction, but it sort of hooks itself onto any foothold it can find, but doesn't really penetrate into the subsurface much if at all. But with gas, oil, heat, and pressure right there, and the pit runs from chamber to beyond the gasket, I would expect the petroleum residue to creep under the epoxy eventually. Cast iron is porous and would wick gas and oil under the repair, I think, and eventually defeat the bond. Maybe not, but since you have a machine shop handy, I would use it.

You will be happier with a permanent fix.

[BrianZ]

The slip fit exhaust coupling for the Dirt Squirt is P/N 939192. Since the first two digits of this part are 93, it tells us that it originated on the model 93, so we know the Super Rat also used this exhaust coupling. Checking my Super Rat reveals that it indeed uses the same part.

As you have already discovered, the model 94 has a larger exhaust spigot.

Brian

[Charlie R]

Hey Max! Here's my nickles worth (inflation you know). I looked at the pic and it appears that the corrosion pits are VERY shallow and do not extend from the bore to the outside of the deck. Is that correct? If so and it were mine I might have my machinist (that's me) skim the surface of the deck to remove the pitting. That should not appreciably increase the CR or affect piston clearance but of course it should be checked. I might also consider surface lapping the deck surface and running it like it is.

At the risk of starting a debate as to the pros and cons of the matter, I apply a skim coat of HT RTV on both surfaces of new head gaskets on every Hodaka engine I build. I mean after all, Webco said not to use a head gasket at all with their performance heads right?

Anyways, that's my 6 3/4 cents worth.....

[hodakamax]

Wow, I need to make three replies--I thought everyone had left town! AZ, you're correct, might as well fix it right, our machinist is quite capable of doing this right or telling me he can't. Hey Brian, this is all starting to make sense, (although I keep finding this 902508 number for all 93s on the SH schematics--That's what was throwing me off). I must have been ordering 939192 exhaust couplings for our pipe fab man. Hard to remember everything that happened 45 years ago! And Charlie, the pits are deeper than they look. this machinist is first class, he's going to bore it also and he's reasonable. I'm sure he can fix the deck OK. Wow, I never heard about using HT RTV on the head. Of course I'm 45 years behind in this Hodaka business! I didn't even know they made HT versions of RTV.
Hey gang, I DO appreciate everyones input--Thanks again!
As always--

Maxie

PS--Ah ha, Bob and Brian, I see what I was doing. On the schematics if you look for exhaust nut for 93s and go to Parts List "A", It shows 908508 for the nut. If you scroll down to "R2" that shows the exhaust pipe, it does indeed show the nut to be 939192. Mystery solved!

[hodakamax]

Edited


Maxie

[hodakamax]

OK, here's another thing I can't remember from 45 years ago. I've found a 93 cylinder and Webco head. Which piston do I need, high or low crown? The cylinder will probably be ported by me for a reed. I want a single ring piston and I can make it holey if necessary, although the Wisceo slotted pistons are probably the way to go. My thinking is that the Webco head was for Ace 100s with high crowns before model 93s and might be lower compression with a 93 piston.
The second part of the question would be, If I need to mill the head, any estimates of how much? The Webco head has been somewhat "fragged" and needs a little cleaning up which will add a little to the equation of restoring the combustion chamber.

Maxie

[hodakamax]

OK, the Day One Project is not dead, just slow. I think it's evolving into a not- too-serious trials/play bike. I was reading some Harry Taylor stuff on leveling the 24mm carb on trials applications. I did a little mock-up on this and wondering if this is still a good path to follow. Another question-- I still have concerns on the post above about the use of the Webco head and high or low domed piston. It's been a long time ago since I sold Webco heads but as I remember it they were for stock 90 and 100s with high domed pistons. Was there a later Webco head that had a blank place for an extra plug and perhaps higher compression for low dome pistons? I'm lost! I guess I could CC it and compare it to other Hodaka heads but It's easier to ask first. Any Input?

Thanks Gang!

Maxie

[RichardMott]

I have a Webco HC head on my trials bike. It was installed by my dealer in 1974. It has a compression release spark plug hole. Here is a photo.

[MWL]

Rick
It would be interesting to know what the compression is with the webco head and which piston you are using?

[RichardMott]

The piston is a D-ring Super Rat reeded. The reed kit was done in 1974 at the same time. As for compression, I don't know. I have a compression tester, but have not tested it. The compression ratio is probably slightly higher than the stock Ace 100B+, but what that is exactly, beats me. I like the Webco head because I think it might provide better cooling due to the fact it has more surface area and mass.
But....there is always a but, does it really make any obvious difference in performance? It might even make the bike top heavy as the photo shows.

[hodakamax]

Hmmm, I hadn't even considered the tip-over factor.

Maxie

[michael_perrett]

That helium in the tires does not help either.

Mike

[hodakamax]

Sounds like a recipe for getting up-side down.

[Zyx]

Rick,

Weren't you supposed to just ride over the obstacle instead of flat tracking it? Can only see the folks behind you from the knees down, but I bet they were clapping like mad.

[hodakamax]

OK, I'm getting into the mock-up phase of the Project which probably will be a Trials/Fun bike and not too extreme. I want a spark arrestor/semi quiet exhaust so I might go with a 94A exhaust. Since I have to build a new header pipe I'm considering lengthening the pipe for more low end power. The cylinder is 93 with a 939192 Exhaust joint. I might try to get Charlie R to build a kinky header pipe to gain 4-6 inches which might be a fun report in itself.

That's the continuing mini-report for now.

Max

PS---Part of the theme is to recycle (so to speak) some of the stuff that has accumulated between a friend and myself through the years.

[racerclam]

I woudnt recommend using that squirt pipe in the picture , If you ride under load for extended periods you will incure detonation , it will cause over heating with a pumped uo engine , so if you want to repair it for a wall hanging thats ok. Bill Cook has reproduction 93 Super Rat pipes , A waaaay better way to go, Even for trials it will work better than the squirt pipe. You just need to find a silencer to make it quiet,

Rich