Cylinder Head

twinegar · Post by **twinegar** » Wed Jul 02, 2008 10:35 am

Is the cylinder head off a 81 X the same as for the 79?
Thanks

EMS · Post by **EMS** » Wed Jul 02, 2008 10:41 am

Other than the color, the valve seats were wider - 1mm vs 0.7mm.

twinegar · Post by **twinegar** » Wed Jul 02, 2008 10:48 am

Would there be a loss of horsepower and is the 81 an improved design because of the wider seats?

EMS · Post by **EMS** » Wed Jul 02, 2008 10:55 am

The wider valve seats were introduced to improve durability in that area. The compression and other performance factors are the same, provided you use the 79 cams. Actually you need only use the intake cams. The exhaust cams in the 81 head are the same as in the 1979 - different from 1980.
The difference in horsepower rating between a 1981/82 and 1979 motor is only 3-5 hp (depending who you believe). I have my doubts, that you would ever feel this in the seat of your pants. Consider that any combustion engine production has a horsepower tolerance of 5-7%.

twinegar · Post by **twinegar** » Wed Jul 02, 2008 11:14 am

I will need to use my 79 intake and exhaust cams. I don't have to have the 81 intake cams? Just want to be sure before I lay out the cash.

EMS · Post by **EMS** » Wed Jul 02, 2008 1:39 pm

twinegar wrote:I will need to use my 79 intake and exhaust cams. I don't have to have the 81 intake cams? Just want to be sure before I lay out the cash.

that will be perfectly fine. You don't need 81 cams for the ehad.

daves79x · Post by **daves79x** » Wed Jul 02, 2008 5:51 pm

You also need to know that the center four head studs are 10mm on the '81 and only 8mm on the '79. Not sure if the copper sealing washers will seal that much larger hole than the stud. Has anyone done that and can tell us?

Dave

daves79x · Post by **daves79x** » Wed Jul 02, 2008 7:09 pm

One other thing if you are buying a head - make sure you get the cam caps. They are mated to the head. You could probably use your '79 ones if you carefully checked them, but they were made to stay with each head. Also make sure the cam bearing surfaces aren't worn past spec.

Dave

twinegar · Post by **twinegar** » Wed Jul 02, 2008 7:25 pm

Will do.
Thanks.

twinegar · Post by **twinegar** » Wed Jul 02, 2008 7:34 pm

I took the X in this post out today for a few minutes and it is amazing how well it runs and how quiet it is until it gets hot. None of the noise appeared but I was only out long enough for the exhaust system to reach running temp. The feel of the engine through the handlebars is addictive.