1978 Standard VS. 1980 Special

[switz1]

Have both bikes any advantages or disadvantages to these two 1100 motors?
Heads, carbs, cams differences?

[TopCatGr58]

Oh boy, here we go!

78E considered fastest version=hotter cams but smaller valves, more tunable carbs, higher comp ratio 9.2:1, also easier adjustable ignition timing plate; kickstarter;

80SG: Larger valves but not as hot of cams; slightly lower comp ratio IIRC 9.0:1 not as easy to tune carbs ie. the slide needle only 1 setting unless adding washers; annoying breakoff bolts on timing plate, can be replaced with regular type;NO kickstarter.

Some folks like to mix and match, putting the 80 head/valves on the 78 engine with 78 cams.YMMV!

[Pat Kelly]

I have one of each. My E was quicker (accelleration) and faster (top speed) than my LG until I did my big bore kit on the LG.
Now the LG is much quicker but the E is still faster.
The top speed is a moot point as I seldom go to those extremes anymore.

[switz1]

Not really debating just wanted to know some advan/dis between the two. Thanks TC and Pat

[Meatloaf]

I've owned both in stock form, a mint 80 and a slightly beaten-up 78. I'm not up on the technical specifics but the '78 blows the doors off the 80 performance-wise. I owned the 80 first and was shocked when I drove the '78.

[saddle up]

So can you slip a 78,79 cams in an 80 head? Or is there going to be a collision?

[trbig]

So can you slip a 78,79 cams in an 80 head?

Works very nicley I might say!! The hotter cams with the bigger valves does well.


Tod

[wingnut]

Are the 79 cams the same as the 78s? I have a set that I was thinking of putting in my 81

[trbig]

Yup... same part numbers. I would think they are fine, but you could MIC them first to be sure they aren't worn too bad or anything.



Tod

[wingnut]

Thanks Tod I'll do that. Donner engine only had 13 K on it and they look good. Did you have to do any rejet or timing changes?

Dave

[trbig]

I didn't have to. Every bike is different. Just like when I put the pod filters on, I only needed one size bigger on main. BUT... you shouldn't have to. You aren't changing the amount of fuel/air flow really... just the time, duration, and height they are operating. Just make sure you check your valve clearance with the new cams.

Timing... don't get me lying. The XJ is electronic, so I don't have to mess with that. Someone else may be able to chime in here and answer that.

Tod

[wingnut]

The SH has a fixed timing plate and the advance is in the TCI like the XJ sort of so I don't expect to have to do anything there. Checking the valve clearance would be a must do. The jets I'll have to play by ear like you said. The bike is bone stock except for the main needles which are up .020. I did that to correct some of the lean problems that came with the emissions thing Yamaha did in the 80s. Yep I think I'll go for it. As soon as the weather turns though. Fall is primo ride time around here.

[saddle up]

Soooo, Would it be a safe assumption to keep the valve lash the same on the later head with the earlier cams?

By the way this web site is the greatest. Thanks to the combined knowledge of XS lovers.

I love it when the young fellows at work give me a ration. I like to point out that the bike is older than they are. lol

[MAXIMAN]

Tod

Ever done a compression test since you rebuilt?

Didn't you couple early pistons with a late head?

[GNEPIG]

Quote:
Soooo, Would it be a safe assumption to keep the valve lash the same on the later head with the earlier cams?

The old and new cams have different settings, You would use the settings that go with the cams = old cams, old settings.

Like Tod has said every bike is a little different, Your jetting may change a little.