Topic: 1972 CB750K2 (start from scratch) project. Cases back together

[Davez134]

Davez134.
I'd be interested to hear your thoughts about how all the modifications you have made to your engine have improved the performance and enjoyment of riding the machine? Was it all worth it?.
Have followed your build story from the other side of the planet with interest.
Cheers

So far, the performance of the engine is great. I have not taken it past 6000 rpm yet, as I have just over 100 miles on it. Also I have never ridden one with a stock motor before, but compared to my last bike with 836cc, non-ported head, stock cam, this one has noticeably more power. With the ported head and webcam 41, it is very practical to ride daily on the street. To me, it was worth it, not so much for the extra horsepower, but knowing that I have gone through every part of the motor. I know that everything was done right, nothing was half assed, and I know I will be able to enjoy riding it for a long time with no issues. That was worth the most to me. Also all the money I saved on a shrink. This is my therapy

[Davez134]

Well, everything was going too good. Have a leak around base gasket. Front left, right where stud is. Not too bad but was really hoping to be leak free!! Damnit.

Wiped clean in the pic, but coking from here


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[Ravie]

That sucks. Almost makes you wanna cry doesn't it?

[Davez134]

That sucks. Almost makes you wanna cry doesn't it?

Yes very frustrated. Spent so much time trying to prevent this. Especially all the way down at base gasket. All I can think of is thicker weight oil and re torquing studs. I have kibblewhite HD studs torqued to 20 ft/lbs and max is 22. Might try it since I have frame kit installed.

[SOHC4 Cafe Racer Fan]

That sucks. Almost makes you wanna cry doesn't it?

Yes very frustrated. Spent so much time trying to prevent this. Especially all the way down at base gasket. All I can think of is thicker weight oil and re torquing studs. I have kibblewhite HD studs torqued to 20 ft/lbs and max is 22. Might try it since I have frame kit installed.

That sucks.  I had a base gasket leak on my 550, and I ended up using HD studs and fixed the leak.  I would give re-torqueing the studs at 22 ft/lbs AND maybe a new base gasket a shot before having to pull the motor and re-deck surfaces.

[Davez134]

That sucks. Almost makes you wanna cry doesn't it?

Yes very frustrated. Spent so much time trying to prevent this. Especially all the way down at base gasket. All I can think of is thicker weight oil and re torquing studs. I have kibblewhite HD studs torqued to 20 ft/lbs and max is 22. Might try it since I have frame kit installed.

That sucks.  I had a base gasket leak on my 550, and I ended up using HD studs and fixed the leak.  I would give re-torqueing the studs at 22 ft/lbs AND maybe a new base gasket a shot before having to pull the motor and re-deck surfaces.

Going to try going to 22 ft lbs first, then if that doesn't stop it I'll pull head and jugs to try new gasket. I have mls head gasket, would I have to replace? Keep same piston rings?

[Davez134]

Cal, in Las Vegas. And if I do anything drastic, I'm going all out. Taking it out to the desert for a bonfire!!

[SOHC4 Cafe Racer Fan]

There are lots of bodies buried in the desert.  Hopefully, this bike won't suffer the same fate!

[edwardmorris]

I haven't gone back and read, but did you use a sealant on the base gasket?

[Davez134]

I haven't gone back and read, but did you use a sealant on the base gasket?

I did not, read on their site to install dry. Wish I would have though. If I end up replacing, I definately will

[edwardmorris]

Sorry for your troubles. From what I've been reading, it seems like installing gaskets dry is the way to go when both contact surfaces have been decked. Otherwise some sealer is almost necessary. I'll be using permatex #2 non hardening sealer when I get to mine, soon. Lets hope the higher torque squeezes this one shut for you, I can only imagine the frustration of getting the sweet taste of riding only to have it taken away, even if its temp.

[Davez134]

Sorry for your troubles. From what I've been reading, it seems like installing gaskets dry is the way to go when both contact surfaces have been decked. Otherwise some sealer is almost necessary. I'll be using permatex #2 non hardening sealer when I get to mine, soon. Lets hope the higher torque squeezes this one shut for you, I can only imagine the frustration of getting the sweet taste of riding only to have it taken away, even if its temp.

Got a new base gasket on order just in case. Don't want to do it, but know how it goes if I have to.

[hotdog]

Bummer, did you coat the base gasket with anything Dave.?
Edit - Sorry have just seen this asked above....

[MRieck]

What type of base gasket did you use Dave? Viton/steel or fiber?

[Davez134]

What type of base gasket did you use Dave? Viton/steel or fiber?

Mike, I used the steel/viton base gasket

I'm wondering, If I need to replace gasket, do I need to replace piston rings as well? Do they seat against cylinder wall a certain way? Or do the rings rotate around in their grooves anyway? I only have 150 miles on this thing!

[hotdog]

Only the gasket Dave, rings will be fine.

[MRieck]

What type of base gasket did you use Dave? Viton/steel or fiber?

Mike, I used the steel/viton base gasket

I'm wondering, If I need to replace gasket, do I need to replace piston rings as well? Do they seat against cylinder wall a certain way? Or do the rings rotate around in their grooves anyway? I only have 150 miles on this thing!

You need to use a small amount of 1194 around the cam tunnel and oil return "triangles". I have used the viton/steel on my FJ and found i HAVE too use it on the right side of the base gasket around the oil feed to the head. It will leak otherwise.

[Davez134]

Got it. I used a fiber gasket on my last one coated with a copper spray sealant, no leaking issues. I may just do that again. Only reason I used the steel/viton one was that it came with the cycleX kit I orders. What are the advantages of that one? So far I see none haha. I'm going to ride it for a few months though. Leak is very minor and I'm being really picky. The thing runs waaaay to good to just take it back down already. When the temps here get into the 100's I'll fix it. Final pics up in a couple days!

[Ravie]

I was kicking around doing the copper spray instead of aviation permatex like I've been planning. Hmmm.

[timbo750]

What type of base gasket did you use Dave? Viton/steel or fiber?

Mike, I used the steel/viton base gasket

I'm wondering, If I need to replace gasket, do I need to replace piston rings as well? Do they seat against cylinder wall a certain way? Or do the rings rotate around in their grooves anyway? I only have 150 miles on this thing!

You need to use a small amount of 1194 around the cam tunnel and oil return "triangles". I have used the viton/steel on my FJ and found i HAVE too use it on the right side of the base gasket around the oil feed to the head. It will leak otherwise.

Mike, can you tell me what the next best thing is to ghe 1194? It does not seem to be available here in Aus. I can get 1104NEO and 1211 but the 1211 is very expensive compared to the others.

[hotdog]

What type of base gasket did you use Dave? Viton/steel or fiber?

Mike, I used the steel/viton base gasket

I'm wondering, If I need to replace gasket, do I need to replace piston rings as well? Do they seat against cylinder wall a certain way? Or do the rings rotate around in their grooves anyway? I only have 150 miles on this thing!

You need to use a small amount of 1194 around the cam tunnel and oil return "triangles". I have used the viton/steel on my FJ and found i HAVE too use it on the right side of the base gasket around the oil feed to the head. It will leak otherwise.

Mike, can you tell me what the next best thing is to ghe 1194? It does not seem to be available here in Aus. I can get 1104NEO and 1211 but the 1211 is very expensive compared to the others.

Timbo, my 2c. - Threebond 1211 is all I use and all I ever will use. Designed specifically for motorcycles, snowmobile, ATV's etc. It can be used on head gaskets as it has a 100 deg Celsius (250c) higher rating than the 1104 it also has a longer working time before it tacks off. Only ever used 1104 once and it wasn't for me.

[timbo750]

Thanks hotdog and sorry dave for temporary highjack. We shall now return to the normal running of this build thread.

[Davez134]

So, I'm calling this bike done! Re torqued studs, put 20w50 oil in there (it is upper 80's today!) and went on a ride with the wife for lunch. Looks dry at base gasket. So here's a summary and some pics:

Started with this

And

Motor gone through 100%, Trans inspected, cleaned, bearings replaced. HD primary and cam chains, cycleX tensioners, New rod and crank bearings, new rod bolts, 836cc wiseco pistons, JMR ported head, webcam 41, cycleX clutch, HD kibblewhite studs, painted wrinkle black and cast aluminum.


Carbs sourced locally and rebuilt/painted


Frame kit, tapered steering bearings, bronze swingarm bushings, new grease fittings

Forks sourced here, polished, new tubes, progressive springs

Hagon rear shocks, rebuilt front brake, slingshot cycles braided lines. All new wiring, pamco ignition, ricks reg/rec, led signals, Here she is now:










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[iron_worker]

Dang! She's a looker. 

Did you end up using sealer on your base gasket and/or head gasket? Did you stick with the MLS? I ask because I've also had some trouble getting my MLS gasket to seal up completely.

IW

[Davez134]

I did not use sealer on either. Base gasket seems ok now after re torque, we will wait and see. Head gasket has been leak free since first start-up no issues there. I did have head and cylinder surfaces trued though.