'78 Head Casting Number Question


Information and questions on GL1000 Goldwings (1975-1979)
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pmacddd
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'78 Head Casting Number Question

Post by pmacddd »



Recently replaced the right head on my '78, due to bending a valve when one cam belt tensioner lost a bolt. That has all been resolved, timing redone, valve clearance complete, carb sync done. When it's running at a constant rpm for a few seconds (3K or better, at least that's where I'm testing) while sitting on the centerstand, and then I give it more gas the engine sputters and sounds like it's starved. Swapped out the fuel filter, and opened the air filter also.

This problem started after the head change, which was supposed to be off a '78 also. The casting numbers on the original are 2BR(?) & 3J, on the replacement 1FFX & 7L. I haven't a clue what casting numbers should be or how to define them, and do they make a difference. Hoping one of the resident wizards on here can shed some light.

This bike was a daily commuter for 3 years, running great, before the tensioner incident a couple of months ago, so I am pretty confident in the carbs, which were rebuilt with Randakk parts before being placed into service as a commuter. Suggestions?


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DenverWinger
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Re: '78 Head Casting Number Question

Post by DenverWinger »

I really doubt it has anything to do with the head, if the new one is the same year the cam grind should be the same.

In spite of the recent rebuild I'd suspect fuel/carb issue. Maybe a weak pump?
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
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pmacddd
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Re: '78 Head Casting Number Question

Post by pmacddd »

Thanks, I guess the head question was more of someone saying it's a '78, and is it really a '78? I have no knowledge to know better.

I had a thought about the fuel pump. I replaced it with a new one when I resurrected the bike, and put it on the road. I have a car fuel pressure tester, but I guess I need to see if it will measure pressure on a bike. Thanks.
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dingdong
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Re: '78 Head Casting Number Question

Post by dingdong »

The head castings are the same for 75 / 79. There are differences in the cams however.
Sounds to me like a problem with the points or even the timing advance. (Was the head on the left the one you replaced?)
pmacddd
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Re: '78 Head Casting Number Question

Post by pmacddd »

Replaced the right head. The reason for my question included the cam question, sort of. Wondering if there are markings I can check to verify the cam.

Used Randakks timing dial to set timing dynamically. I remember the advance working, have to think it was right or I would have done something. Good idea though and maybe I need to check again. Using Dyna ignition.
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DenverWinger
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Re: '78 Head Casting Number Question

Post by DenverWinger »

If there's doubt about having the correct cam in the right head, if you still have it you could swap in the cam from the original head.

Having said that, if you have a cam from a different year with a different grind, I don't think that would cause the engine to stumble and falter as you describe, even though the different grind would change the performance characteristics of the right two cylinders.

Leads us back to carburetion/fuel/other issue.
♫ 99 Little Bugs in the Code, ♪
♪ 99 Bugs in the Code. ♫ :(
♫ Take one down, Patch it around, ♪
♫ 127 Little Bugs in the Code. ♫ ♪ :shock:

~Mark
pmacddd
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Re: '78 Head Casting Number Question

Post by pmacddd »

Yeah, guess I need to just back up and go through it all again. Thanks guys.
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Re: '78 Head Casting Number Question

Post by Old Fogey »

Cams from 75-77 have no marking other than L or R ( why they have that I don't know, as it's quite obvious which is which). Cams from 78-79 have 431 stamped on them and are different timing from the early version.


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