tourqe specs

[bronco70]

getting prepared to install clyinder on 125cc combat could anybody supply torque specs

[racerclam]

the manual specs are wrong , Harry Taylor had told me to torque to 220 inch lbs .

Rich

[Bullfrog]

A slightly different way of saying it would be . . . the original 1970's era torque specification for the cylinder head nuts was 170 in/lbs. Over the years, with considerable testing, it was discovered that base gasket and head gasket leaks could be reduced by using a higher torque specification. Testing also confirmed that the size of the cylinder stud threads and the structure of the cases at the base of the studs are capable of handling a considerably higher torque specification. So Harry Taylor (former Hodaka Research and Development guru) became quite comfortable with the following torque specification for all of 125cc Hodaka engine cylinder head nuts:

For full blown, heavily modified, high output 125cc racing engines - 300 in/lbs

Your friendly local former head of the Hodaka Service and Warranty Department is somewhat more comfortable with 250 in/lbs for generally stock or lightly modified 125cc engines (and I had not heard till just now that HT had told Richard that 220 would be OK).

Summary: Use 220 or 250 in/lbs as the "new, improved" cylinder head torque specification for stock or lightly modified Hodaka 125cc engines.

CAUTION: DO NOT use this new specification on the "Ace" series 100cc engines.

Ed

[TheBevman]

Good to know, I just put my Wombat (94) together and just re-torqued the head to 170 in/lbs. I assembled it with a greased base gasket and the copper spray stuff on the head gasket, in hopes of helping it seal. Leak check was perfect but know you have me thinking that I might need to torque it a bit more now.

Thanks for the added info Ed.

Bev

[Bill2001]

Thanks Ed and Rich. Good info. BMW (factory and enthusiasts) are nutcases for "proper" torque. Tables of torque values for every bolt.

That head bolt value seemed a bit light to my TLAR sense. I'm slowly compiling a list of values-- mainly for the noob wrenches, who don't yet have a calibrated wrist.

[bronco70]

thanks guys just waiting for my gaskets to come in now
1 more dumb ? i only have ft lb wrench would i be right
saying that 220 in lbs converts to 18 ft lbs?

[matt glascock]

Correct 220 divided by 12 = 18.3. Quick question, Captain. Do you include Model 93 Super Rat motors with the Ace series 100cc engines when discussing torque specs? I'm about to freshen up the top end with new rings and gasket. It now is on its 1st overbore, is ported for reed valve induction, and is running (very well) at about 158 PSI compression.

[dcooke007]

.....and don't forget to retorque head bolts after a few heat cycles. You will be surprised.

Danny

[Bullfrog]

Yes, the language choice was quite purposeful - the toaster tank Super Rat engine IS an Ace series engine with smaller cylinder studs. So the higher torques mentioned for the 125cc engines are NOT recommended for the toaster tank Super Rat engine.

Since I suspect the next question will be, "What about the painted tank Super Rat engine (Model 98)?" Since it has the 8mm cylinder studs common to the 125cc engines, the higher torques could be used for it. (. . . and it is not an Ace series engine - all of which have 6mm cylinder studs, iron cylinder, small crank, etc.)

Ed
PS: What Danny said about re-torqueing after a few heat cycles. Yes!

[bronco70]

Great thanks again guys

[racerclam]

Just to mention that my Super combat has 200psi compression and does not leak with 220inch lbs torque and I do use some silver paint on the gasket. and with the origonal specs it did leak

Rich

[matt glascock]

Thank you Captain, et al. 170 in/lbs it is.

[Bullfrog]

Matt,

Huh????

The whole thread is about NOT 170 in/lbs.

So I say again, Huh?
Ed

[matt glascock]

Captain, could you believe that my typing is so bad that while aiming for the 2, 5, and 0 keys I hit the 1, 7, and 0 keys instead? Didn't think so. Maybe I'll add paying attention to my M.O.

[Bullfrog]

So the thread didn't exactly meet the requirements of riveting reading for you?

I'm working hard on the excuse . . . off by one on the 2 and the 1 keys . . . only off by two on the 5 and the 7 keys . . . and finally nailed it on the 0 key. Mmmmmmmaaaaaayyyyybe . . . but . . .

Ed

[relic]

And while we are on the subject can I ask about the B+ head/cylinder nut torque please? Book calls for 105 in/lbs --- is this still the recommended torque?

And thought I'd add a reminder regarding RE torquing --- this doesn't mean setting your wrench at the spec and seeing if the nuts turn some more. Proper retorque technique is to first loosen the fastener and then bring it back up to the proper torque. If you are curious to know if it has turned further, mark the fastener head and the cyl hd for reference.

Ken

[Hydraulic Jack]

A question arises from this discussion: would it not be possible to install the larger diameter cylinder studs in the earlier cases by drilling and retapping the cases to the 8mm spec? Side by side inspection of the stub boss area would be needed, but if the case molds were basically the same between early and later models, why could we not upgrade the cylinder studs, and then use the higher torque values on the Ace series?

[taber hodaka]

Here is where I would value various professional opinions. I would retorque after a few heat cycles. But in that stage I would not loosen first and then retorque?? I have not had head leakage problems on the ace 90 or up to the ace 100B+. -----Clarence

[Bullfrog]

The Ace series engine(s) cylinder head nut torque specification remains unchanged - 105 in/lbs.

As they say, "the devil is in the details" . . . and no I don't think it would work to change the Ace series engines to 8mm cylinder studs. But then there is no need - folks just don't have problems with the Ace series of engines with the 105 in/lb specification for head nut torque.

Ed

[relic]

Thanks Ed. Just wanted to check if thoughts had changed on the Ace100's. Clarence, I mentioned the retorque method as its something I was taught in trade school many years back and have read in most service manuals when a retorque is called for. Maybe its more important on higher torque specs? I don't know but its definitely something that's in the manuals these days. As you say, probably not important for our Hodaka engines.
Ken

[matt glascock]

Just drilling down on the "0" key, Captain. Took me three tries to hit the intended mark.

[Bill2001]

The way I retorque is to loosen about 1/4 turn and retorque in sequence at 1/3 of the final torque in steps (10-20-30 for example.

I don't use paint or copper coat on the head gasket. Mostly we use composite gaskets. The sheet aluminum are usd only on Hodies or lawnmowers.

What is the concensus on silver paint or copper cote? Remember, the Aluminium head gasket will have the same thermal expansion as the Al.head, and three times that of an iron cylinder. There will be differential expansion betw the gasket and cylinder.

[TheBevman]

I really enjoy reading threads like this, they're very informative to other's techniques and habits.

That said, I'll put my 2cents in on your question Bill, I always use copper coat on head gaskets unless:

1) the manual strictly advises against it or 2) its a copper or aluminum gasket that needs to be annealed prior to installation.

I figure its a little added insurance against leaks and the copper coat is still tacky enough to hold the gasket during installation, not something as important on bikes as it is on other engines. Also, I always grease paper gaskets too because it holds them and keeps them from drying out, well for a bit, or sticking and tearing during disassembly so you can reuse them. That said, I wouldn't re-use a head or base gasket.

Bev

[dcooke007]

I have pressure test a few Hodaka engines and developed processes that work for me. The more engines you pressure test the more you learn where the common air leaks are.

On the head bolt retorque I do not loosen but simply retorque. Most of the time the bolt will rotate 1/8 to 1/4 turn. I am also careful to lap the cylinder and head gaskets surfaces flat before assembly.

I have tried a couple of sealers and have settled on Copper Coat. Base, head and intake manifold gaskets are coated on both sides. The Copper Coat stays kind of tacky on the paper gaskets and helps with easy removal. Not sure you would be able to reuse the gasket a second time though. I don't use Copper Coat on the clutch cover gasket so I can remove and reuse it.....just oil gasket.

Besides gaskets there are two other common sources of air leaks. Head bolt studs being one. I always remove the studs from the engine cases and run a die / tap over the stud and engine case threads. Apply red locktite to seal and reinstall studs. The second air leak occurs at the engine case halves. Before installing the cylinder base gasket I apply a dab of rtv sealer to the area where the two case halves meet and then install cylinder base gasket. You could also use a dab of Yamabond instead. Only using 190 inch pounds torque on the 125's at this time. This is sop for me.

When pressure testing sometimes air leaks past the spark plug threads and prevents proper testing. I have found using Teflon thread tape on the spark plug threads stops the leak. Remove tape after pressure testing.

Danny Cooke

[Hydraulic Jack]

Danny,

I agree with your established procedures. Time and repetition proves our theories. I question, however, the Teflon tape on the spark plug. Assuming one uses the tape to prevent a potential leak so we can properly test other areas, still, if it needs Teflon to seal, once removed, you reintroduce the potential for leakage and leave an untested unknown. I would test every area of potential leakage in the condition it is going to be run. Otherwise, why test at all?