Topic: CB125 Cylinder Head Stud Installation Question??

[natez]

I'm putting my cylinder and head back on after splitting the case to bore out the spigot to accept my new 145cc cylinder.

I removed the cylinder studs to do all this. My Clymer manual doesn't give instructions on installing these studs, only the proper torque. Which direction do they go in? The threads are shorter on one end...

Thanks!!

[eigenvector]

edited
shorter threads go into the case...

Remember the head is going to squish down a bit as you torque it, so you need a bit more purchase on the bolt - hence the longer end up.  Not mention there will be a thrust washer under the nut so you need more thread anyway.

Don't forget to threadlock the studs into the case or you'll unscrew them if you ever have to loosen the head bolts.

[natez]

I saw pics/videos online that showed both ways, so I wanted to get it right! Thank you.

[eigenvector]

Dry fit first please...

That is, don't button it all up, lock the threads, put on a new head gasket, bottom gasket, etc before you've fitted it all together.  Save yourself a lot of agony that way.

[natez]

Happen to know the torque? I think my book says 13ftlbs, however it doesn't call the studs "studs" and while winding it up to 13ftlbs I was getting scared of stripping the soft aluminum...


ALSO, my LEFT (edited) side studs can go all the way down into the case and touch the crank if you wind it that far... whats up with that? How would I torque those?

[grcamna2]

What model/yr. engine number is your engine? you using the exact same studs as before ? any pics of both ends of the studs ? The 2) shorter studs go on the right side(spark plug side)of the cylinder where the oil passage is.

[natez]

Geez I didn't even notice that they were two different sizes... yes I'm using the same exact studs that I pulled out of the engine. Its a CB125S(E), I believe it to be a '78, '79 or '80 model year. It has the older rotor that spins inside the stator. Why isn't this stuff in my manual?

Also what am I going to do with the studs on the left side that screw all the way down into the case?

[grcamna2]

The cylinder studs get installed with the long threads into the cases and the little 'rib' at the end of each set of threads is where they bottom-out on the cases;the 2) long studs on the cam sprocket/Left side and the 2) short studs on the right(spark plug)side.I don't use loctite myself as they lock-down well into the cases w/o it. Merry Christmas

edit:Will you be using that 'CB145cc 61mm cylinder/piston kit' off Ebay? if so I recommend you use the oem stock replacement aluminum shim head gasket for the XL185 (63mm;it will bring the compression ratio back down to about 10:1)from your Honda dealer as that piston has too much compression(like 11.8:1 !)for your engine and can easily strip your kickstarter ratchet gears trying to start it and cause the engine to ping bad w/o retarding the ign. timing less than the 'F' mark.. which defeats the power increase the kit gives you.
I did that mod. to my little CB125S and used the kit head gasket that it came with and those are the problems I had.

[scottly]

Happen to know the torque? I think my book says 13ftlbs, however it doesn't call the studs "studs" and while winding it up to 13ftlbs I was getting scared of stripping the soft aluminum...

The soft aluminum case is the reason the longer threaded ends of the studs go into the case, like grcamna2 says. The torque spec is for the steel nuts that hold the head down, not screwing the studs into the case.

[eigenvector]

Glad someone who knows better chimed in.

[natez]

What is the correct torque??

[natez]

grcamna2, also do you happen to have the honda part number for that head gasket? Yes, that is the kit I am using. Great info I would have found out the hard way! Any other tips about the install? (carb jetting, etc)

[grcamna2]

Happen to know the torque? I think my book says 13ftlbs, however it doesn't call the studs "studs" and while winding it up to 13ftlbs I was getting scared of stripping the soft aluminum...

The soft aluminum case is the reason the longer threaded ends of the studs go into the case, like grcamna2 says. The torque spec is for the steel nuts that hold the head down, not screwing the studs into the case.

Nate,
I install my engine studs w/ an 8mm stud remover/installer(made in Japan) 'socket' looking tool(that has 3 rollers inside that won't damage the threads) that grabs the top threaded parts of ea. stud and then I turn them down into the cases until they 'bottom' at that little 'rib' at the end(you can 'chase' the threads at the top later w/ a metric die to make them sharp again) of the lower/longer threads and then keep tightening until they are snug w/o damaging the stud;they're designed to lock-in very well to your cases w/ a tight fit.I would rather see you use that type of tool rather than Vise Grips as that can damage the studs.That little 'rib' is tapered and will hold each stud in place well;make sure to clean-out/blow-out each threaded hole in your cases so the studs thread in cleanly and lock down securely.

[grcamna2]

grcamna2, also do you happen to have the honda part number for that head gasket? Yes, that is the kit I am using. Great info I would have found out the hard way! Any other tips about the install? (carb jetting, etc)

Yes,
part# 12251-427-P00  (those are 2) zero's/numerals at the end of the part#  ) Sometimes(especially this time of yr.)you can get a deal on parts if you punch-in the part# on Ebay plus free shipping.

I don't know if you can even find one but if you get a right muffler for a CB350K4 twin(#HM344)that isn't rotted-out already... and then get the stock exhaust(#CB125J) front head-pipe for the 76-78' CB125S along with the special #PD66 stock carb/manifold & atomizer plate(this carb. and manifold a Very difficult to find) the bike will run sweet.The CB350 # HM344 right muffler mounts right up exactly to the stock 76'-78' CB125S front pipe using the same stock muffler gasket and clamp as the CB350K4/K5.

[natez]

I'm using the old two nuts locked together trick (you can see them on one of the studs in the above 2nd pic) to tighten the studs, no vice grips here. So your saying just torque them down to a "secure" fit like my manual says for the case bolts and other items with no actual specified torque value?

Do you remember where you started off with your jetting? I imagine I'll be going up a few jet sizes with the bigger jug/piston on it...

[grcamna2]

I'm using the old two nuts locked together trick (you can see them on one of the studs in the above 2nd pic) to tighten the studs, no vice grips here. So your saying just torque them down to a "secure" fit like my manual says for the case bolts and other items with no actual specified torque value?

Do you remember where you started off with your jetting? I imagine I'll be going up a few jet sizes with the bigger jug/piston on it...

The double-nut works well,yes just get them snugged-down good and tight and they'll stay put.
Jetting depends on what exh. you'll be running and whether you modify the airbox/filter.I ran mine w/ a #100 main jet but I like stock exhaust and airbox even though it needed a better breathing exhaust;it'll run hot if you run a restrictive muffler.
Do you have any pics of the carb. and filter you plan on running ?

[natez]

I'll take a pic in a bit, but I'm running a mikuni carb with a cheap ebay cone filter on it and for exhaust I have a custom header pipe to some sort of super-trap/cone style muffler with all the fiberglass taken out of it so its pretty free flowing. Ran great with a 95 main jet and the clip on the needle all the way down.

What did you do about the missing recess for that o-ring on the top of the new cylinder?

[grcamna2]

I'll take a pic in a bit, but I'm running a mikuni carb with a cheap ebay cone filter on it and for exhaust I have a custom header pipe to some sort of super-trap/cone style muffler with all the fiberglass taken out of it so its pretty free flowing. Ran great with a 95 main jet and the clip on the needle all the way down.

What did you do about the missing recess for that o-ring on the top of the new cylinder?

That stock oem Honda XL185S head gasket part# I gave you is meant to run w/o an o-ring on that cylinder stud,it'll tell you in the sheet that comes w/ it.
I recommend running the stock airbox w/ the rubber intake snorkel removed rather than that little cone filter for much better midrange,removing the rubber intake snorkel will give it much more flow and the stock design of the rubber intake tube and airbox will make it run better.I cut-out a piece of universal Unifoam which flows more air and installed it in place of the stock filter foam inside the box.Those little pod filters are more for looks rather than all-around torque/performance,they also let a lot of dirt into your engine which can eat-up your top-end.

[natez]

So your saying I need to get my head machined so I can fit that o-ring? Did you? Interestingly the gasket that came with the kit has the bigger cutout for the o-ring, however no recess in the cylinder for one, however its a fiber gasket with a thin O-ring-material line just inside the edges so maybe it seals better than the metal multilayered one?. 

Gasket is ordered however, $12. 

The old gasket I took out of the motor didn't have the bigger hole for the O-ring, which is why they got away without the O-ring I guess.

Problem is I don't have the airbox parts, never did and my engine is actually in a Kawi KM100 frame so fitting one isn't going to happen. Think I will need bigger than a #100 main jet probably? I have 95 through 125 to fiddle with, will move the clip back to the middle too.

Did you use the same sparkplug or did you end up going with a different part number?

[grcamna2]

You should go w/o the little stud o-ring,check out the instructions in the new head gasket package.
I ran a D9EA and it worked well for me,I used the D8EA to get the jetting within the ballpark first.

[natez]

Ah sorry, I misread your earlier post about it not needing the o-ring, hopefully the gasket will come complete with the instructions. Think I should just go straight to the D9EA?

[grcamna2]

Ah sorry, I misread your earlier post about it not needing the o-ring, hopefully the gasket will come complete with the instructions. Think I should just go straight to the D9EA?

You could foul the D9 if you use too big of a main jet too soon,better to get a few different plugs to do jetting.