GL1000 Engine pieces parts

cross over parts from other wings, hondas, or any other parts sources that can be used on our wings.

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Whiskerfish
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GL1000 Engine pieces parts

#1

Post by Whiskerfish »

GL1000 engine differences

We have had many discussions recently regarding the interchangeability of parts on the 1000 engines. Mixing and matching of 1000 parts happens all the time. Playing with the mix of engine parts is not as simple as “will it bolt up?” Odds are yes it will bolt up and yes it will probably run but that is not the whole story.

The 75 was produced with highest horsepower and peak performance of all the 1000’s and was rated at 84 HP. Each year a few things changed but the dramatic changes happened between the 1977 and 1978 model years. The most common place for these changes were the Carburetors. The changes were driven by the times as Emissions controls were becoming commonplace and by the development of the GL1000 as a touring machine. The Torque curve was flattened to provide more mid-range torque at the expense of some peak HP. Some reports had the 78/79 series as low as 79 or 80 HP.

Carburetion changed every year, the biggest change was from the 77 to the 78 models with the reduction of the venturi size by 1 mm and more changes in the jetting profiles. The CV slides also changed several times with the most dramatic of those changes happening between the 75 and 76 Model years. The 75 slides were shaped at the bottom so when they were raised the entire carb throat was open. The Carb linkage also changed between 75 and 76.

---------------1975---------1976---------1977---------1978---------1978EC---------1979
Venturi bore
Diameter----32mm-------32mm-------32mm-------31mm--------31mm----------31mm

Main Fuel Jets
Pri-------------65-----------62-----------62------------60-----------60--------------60
Sec-----------125----------120----------120-----------120----------120-------------120

Slow Fuel Jet-35-----------35------------35------------35-----------35--------------35

Main Air Jets
Pri------------120----------120-----------120-----------120----------140-------------140
Sec------------60-----------60-------------60------------60-----------60--------------60

Slow Air Jet--110----------115-----------110-----------120----------130-------------130


The Cams, Valve timing, ignition timing, and exhaust system also all changed between the 77 and 78 model years.

The Camshaft peak intake lift was reduced from 37.07- 37.23 in 1977 to 36.72-36.88 in 1978

This reflects the Valve timing changes driven by the reshaping of the cams.
Camshafts-------------1975 - 1977-----------1978 – 1979
Intake opens:----------5 Degrees BTDC-------5 Degrees BTDC
Intake closes:----------50 Degrees ABDC------35 Degrees ABDC
Exhaust opens:---------50 Degrees BBDC------40 Degrees BBDC
Exhaust closes:---------5 Degrees ATDC-------5 Degrees ATDC

The initial Ignition Timing point changed from 5 BTDC in the 75-77 models to 10 degrees BTDC on the 78/79 models. Also the timing advance curve was redesigned by the use of a different timing advance unit mounted behind the points plate. This resulted in the peak advance of 32 degrees being reduced to 27 degrees on the 78/79 model.

The exhaust was completely redesigned in 78 to a 3 piece muffler unit from the single piece Horseshoe. The lack of exhaust noise of the earlier models was a complaint for many owners. The redesign in 78 increased the noise and changed flow characteristics to further the progression toward the touring engine profile and away from the sport/performance model of the earlier years.

Those are the changes that were performance related. Numerous other small changes were made during the various production runs to address other issues. The cases were slightly modified starting in 78 in an effort to mask certain engine noises. And the rear cover was modified in 78 also, removing the kick-starter option.


Everything above is factual to the best of my knowledge. This next part is my advice/opinion/observations.

Each year we get hit with questions like “will my 79 run better with 77 carbs” or “can I improve the performance of my 78 by running 75 heads” or “will my 76 be faster if I switch to straight pipes” or “a guy told me…….” etc etc etc etc etc etc……

If you are trying to get a bike running and all you have are 77 carbs to put on a 79 go for it. Will it run? Yes it will, will it run correctly? No it will not, will it be adequate? Well that is entirely up to you. If you ruin a head and need to replace it then replace it with the same series i.e. 75-77 or 78/79. Do not buy the first one you see on Ebay just because you can’t wait any longer. If you want to bolt on 75 parts to a 78/79 to improve performance then you need to do the whole thing. Carbs, Timing Index, Timing Advance, and Cams. Doing anything less will likely result in a loss of performance vice any supposed gain.

The Engineers that designed these bikes had test equipment we can only dream of, and data built on years of tests and decades of educated experience. The intricacies of ignition timing, fuel air mix, valve timing, combustion chamber flow dynamics, exhaust scavenging all have to be balanced. Bottom line is that I do not doubt that performance improvements can be made to the stock setup, but the odds of getting the right combination by bolting up pieces parts from another model are miniscule. Unless you really really really know what you are doing if you want to get maximum performance from your GL1000 keep it stock and in good tune.
Last edited by Whiskerfish on Wed May 06, 2009 3:50 pm, edited 1 time in total.
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#2

Post by Oldewing »

Thanks WF, nice to see all of this in one place.

Oh and congrats on your new role, (bowing to the new King)
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Whiskerfish
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#3

Post by Whiskerfish »

Oldewing wrote:Oh and congrats on your new role, (bowing to the new King)
Yea well I did not get a pay raise so ya still gotta buy your own beer when we meet up ;) ;) ;) :lol: :lol: :lol: :lol:
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!

Psst. oh and by the way CHANGE YOUR BELTS!!!!
dposer
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Re: GL1000 Engine pieces parts

#4

Post by dposer »

by timing index do you mean the crank? if so is there any way to time it without switching the crank (assuming that you replace all the above)?
1978 gl1000
1982 cb900c
most of a cb900f
1987 toyota mr2
1988 toyota mr2 <--320k still runs strong
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Re: GL1000 Engine pieces parts

#5

Post by CYBORG »

dposer wrote:by timing index do you mean the crank? if so is there any way to time it without switching the crank (assuming that you replace all the above)?
you can use a degree wheel on the front of the crank, and change the timing marks on the flywheel
1978 custom GL1000
1977 custom with 1200 engine
1985 gl1200
dposer
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Re: GL1000 Engine pieces parts

#6

Post by dposer »

but how would i know where to move the marks to? oh and is there and differences in pistons or comp ratio from year to year, i would rather just swap the cams than have to pull the whole head off
1978 gl1000
1982 cb900c
most of a cb900f
1987 toyota mr2
1988 toyota mr2 <--320k still runs strong
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CYBORG
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Re: GL1000 Engine pieces parts

#7

Post by CYBORG »

dposer wrote:but how would i know where to move the marks to? oh and is there and differences in pistons or comp ratio from year to year, i would rather just swap the cams than have to pull the whole head off
the degree wheel that you mount on the front of the crank allows you to see how many degree's you turn the crank. if you start with the timing marks lined up, you then turn the crank the corrrect number of degree's to match up with the change you are trying to make. at that point you mark the flywheel to indicate that difference, so that you can set the timing to the correct number for the new parts.
also i would change the whole head to insure the prober cam bearing surface clearences
1978 custom GL1000
1977 custom with 1200 engine
1985 gl1200
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Re: GL1000 Engine pieces parts

#8

Post by bikerdad5 »

what are the horse power ratings for all 76 and 77 years?
Why should I press one for English?
1977 GL1000 basket case/resurrection project.
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Re: GL1000 Engine pieces parts

#9

Post by dartman1962 »

Thanks guys,

I wanted to ask the question as I wanted to find a spare engine for my 75 model. Up here in Saskatoon & Canada there is not an abundance of these to choose from. So I wanted to know the difference between them.
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