Topic: CB750 /836cc Head Gasket Issue

[captaink]

Hi, Any thoughts on the following appreciated.

I'm in the UK and in the process of building a 1977 k7 engine and its now got a Wiseco 836cc big bore kit fitted.
The Cometic head gasket that came with the Wiseco kit only has two larger (17mm ) hole cut outs for the studs with O rings the rest are just stud clearance size.

My cylinder has the 2 plus 8 more for the knock pins and seals, 10 X 17MM holes are required in total.
The Wiseco kit supplier here in the UK says there's only ever been this gasket which is wrong for me.

The standard gasket kit from David Silvers in the UK has all 10 larger holes but of course the cylinder bore size is standard 750cc and too small.
I have seen gaskets on USA sights but wondered if anyone has any thoughts on this issue

Regards Keith

[seanbarney41]

Most guys Will omit the knock pin and packings that unique to the later engines.  I know, sounds like a bad idea, but several have been successful.  Google up "brandens leak free top end" thread for all the other tips and tricks.

[madmtnmotors]

Most guys Will omit the knock pin and packings that unique to the later engines.  I know, sounds like a bad idea, but several have been successful.  Google up "brandens leak free top end" thread for all the other tips and tricks.

+1

Early motors did not have them. You could run without them or punch the holes out to accommodate them.

[PeWe]

Yamiya750 836 gasket has the larger holes as was more common here before.

MLS gasket is another alternative if both sides are flat and have smooth surfaces. Small holes, no 8 special pins with o-rings on this type either.
Mount gasket dry, no additional sealer. I used copperspray on one cometic fiber and got a huge oil leak despite really good mating surfaces. I changed to MLS after that. MLS keep the head nut/stud torque better.

[Jerry Rxman Griffin aka MuthaF'er]

I'd prefer to keep the additional "o-rings" myself. Can't hurt and may prevent a leak IMO. A hole punch will take care of that minor detail.

[captaink]

Thanks for the replies so far, I would prefer to keep the 8 seals and punch holes larger but there very close to the main piston hole.
I wondered if gaskets were available, Wiseco surely would not have limited there big bore kits to early models only.
More investigation required I think
Cheers

[Terry in Australia]

I think Pewe's right Keith, this looks like what you need.

http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_21_249_51&products_id=757

[greenjeans]

I've used MLS gaskets from Ken's cycle X 4 times now.  I like and would recommend them.  Did not put the rubbers back in.   No leaks.

[PeWe]

I think Pewe's right Keith, this looks like what you need.

http://www.yamiya750.com/index.php?main_page=product_info&cPath=246_21_249_51&products_id=757

Cruzinimage too. I have in stock (in my garage) but has not tried one yet. Have to build an 836....
http://www.ebay.com/itm/69-77-HONDA-CB750K-BIGBORE-HEAD-GASKET-65mm-BORE-SIZE-CI-CB750KGS-1-/162444780167?vxp=mtr&hash=item25d276a287

[Nic]

I have tried both the Yamiya one and the Crusin image one, while the Crusin Image one is way cheaper you will need to retorque after heat cycling the engine, when I did this there was very little torque on the nuts as I retorqued. The Yamiya one is BS expensive but when i went to retorque I found the nuts were still good and no retorquing was needed. I would spend the extra on the CI one every time.
Yamiya also sells the pucks, they sell Yamiya ones and Honda ones, the Yamiya ones are cheap and the thinnest I've seen, stay away from them.

[disco]

I installed the Cruizin Image 836cc pistons, head gasket & Ape HD cylinder studs. Torqued the head down to 18-20 ft/lbs from memory. Re-torqued after 24 hrs.

My cylinders incorporated the additional o-rings & they were installed as per Mr Honda intended. So far, no leaks & no problems at all.

As PeWe stated, the head gasket is available as a separate purchase.