Topic: how can you tell an 836 kit without opening the engine?

[the architect]

So, this guy has a spare CB750 engine for sale.  He didn't specify the year or mileage.  He says it supposedly has an 836 kit on it, but he can't really substantiate that.  Is there any way to verify this without removing the head and measuring the cylinder diameters?  Are ther any give-aways that can be seen through the intake or exhast ports or even the valve adjustment covers?  Anything?

[bucky katt]

there really is no way to tell without pulling the head, you might try a compression test. if i understand my engine theory correctly there will be more than stock cylinder pressure when doing a compression test if there are high compression pistons (most 836 kits have between 10.25 and 10.5:1 compression

[754]

Get a cylinder light or make one using a MagLite bulb, pop a plug and look in. Sometimes with a reg flashlite you can see. With this light you can also see part of the valves and rusty or water damaged bores.

 Pretty well all, built (over 750cc) motors have noticeably BIGGER VALVE cutouts & higher dome, if you see that, a good sign. if you see a lot of meat between the cutout and piston edge.. even better..

 Also if you check valve clearances and they are .005 or larger, it probably  has a hotter cam, you may notice different springs, with valvecaps off. You may have to tell them you are worried about sunken valves..

 Appear not to be excited when you see all three... .. just say looks like it may be bigbore, hope its not 350 pistons!!

[sangyo soichiro]

Or you can make an offer as if it was only a 736.  Tell him that if you can't pull the head and prove it's an 836, then you're only willing to deal as if it's a 736.  Seems fair to me.  You may offer to buy a new gasket I suppose.

[754]

Keep in mind if its 836, could still be wornout, setup improprly , need rings you cant find, etc.. good news, you can then take it to 850cc..

[HavocTurbo]

Or you can make an offer as if it was only a 736.  Tell him that if you can't pull the head and prove it's an 836, then you're only willing to deal as if it's a 736.  Seems fair to me.  You may offer to buy a new gasket I suppose.

Keep in mind if its 836, could still be wornout, setup improprly , need rings you cant find, etc.. good news, you can then take it to 850cc..

Ah yes..... between the two of you.... We'd be buying a 1000 Cobra motor for the cost of 736cc's!!! 

I'll chip in.... ask him to pull the head. You can always get a new head gasket.

[754]

Why pull the head when you can pull 2 plugs..

[ekpent]

Pull the plugs and peek and keep it your little secret if you find the "goodies" 

[Jim F]

I thought I was getting a 944 engine and it turned out to be an 836 After I pulled the head

be careful but at least if you see high done pistons it can only be an 836 or bigger

Jim

[wrenchmuch]

I've had good results putting the light in the intake port with the intake valve open and looking in the plug hole .

[HavocTurbo]

Why pull the head when you can pull 2 plugs..

You're no fun. 




 

[Don R]

My first 836 is an 812, I bet the one the guy said was 936 might even be an 836.  stock cams in both.

[Jerry Rxman Griffin aka MuthaF'er]

Take a valve cover gasket and impact wrench with you. Cheap and plentiful. Pull the valve cover. That's easy. Look at springs, retainers and cam. How many guys bore without camming?!