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Old 02-20-2013, 12:53 PM   #1
gsjoel OP
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Cool2 Starter Covers & Airboxes

I have a 1981 R80 G/S with a 1980 R100 motor in it. This engine has the later model starter cover and flat, plastic air cleaner box, though. Want to convert it back to the old style. I have the parts, but will bolt right up? What do I do about the breather that currently dumps into the air cleaner, and will removing the snorkel setup and changing the filter affect the running in any way?

Thanks in advance,

Joel Parks
Yonkers, NY
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Old 02-20-2013, 02:39 PM   #2
bpeckm
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Yes they will bolt up... but yes, you will want to do something with the oil breather. The old system simply dumped it into one side (right side?), but you can probably come up with something clever.

You do know that the "old style" starter cover was different as well? It takes the starter cover with the curve-upwards, and the round-air-filter air cover. I did it on an R100 just 'cuz I like the looks of the old style....



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Old 02-20-2013, 05:50 PM   #3
Plaka
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Quote:
Originally Posted by gsjoel View Post
I have a 1981 R80 G/S with a 1980 R100 motor in it. This engine has the later model starter cover and flat, plastic air cleaner box, though. Want to convert it back to the old style. I have the parts, but will bolt right up? What do I do about the breather that currently dumps into the air cleaner, and will removing the snorkel setup and changing the filter affect the running in any way?

Thanks in advance,

Joel Parks
Yonkers, NY
The old style airbox, filter and starter cover (must use old style for all three) doesn't breath as well as the new style. So this will leave you running a bit rich. i wouldn't worry about it. Build it, run it and then adjust jetting if needed. Jets are cheap.

if you look at the diagram here you see the windage setup on top of the block. Seems to me part #2 is for the old style with a hose to the Right intake and Part #3 is for the new style.

http://www.ascycles.com/Illustrated_...indCat=11_1725

This shows an old style starter cover and windage assembly. You need it all.

http://www.ascycles.com/Illustrated_...indCat=11_1734

This shows old and new style starter covers. The one with the slots (rather than the scoops) is for the flat airbox)


/crap, lost thye link, well, you'll find it/



The new style windage feeds both sides.




http://www.ascycles.com/Illustrated_...indCat=11_1755
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Old 02-27-2013, 12:05 AM   #4
bmweuro
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If you are using the stock breather set up you will need 79 on air filter housing and these 2 breather hoses 11 15 1 335 733 and 11 15 1 335 734.
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Old 02-27-2013, 03:06 AM   #5
Bill Harris
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Quote:
Originally Posted by bpeckm
I did it on an R100 just 'cuz I like the looks of the old style....
I like to think of this ^^^ as old school

Your bike in the pic? Nice!

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Bill Harris screwed with this post 02-27-2013 at 03:11 AM
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Old 02-27-2013, 03:40 AM   #6
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When Rob Farmer was chasing a mixture problem he fitted a "O2" meter to his RS? which he could read out on the road, and found that the flat filter didnt flow enough at high revs , and stuffed up the mixture.

He fitted a old style round filter which flowed better, and didnt affect the mixture as much at high revs, but it still wasnt perfect.

Last I can recall he was working on modifying a flat filter so it did flow enough.

So he got the opposite result to Plaka.
But I am not saying either is wrong.

Same thing with the snorkel set up - some folks remove them from the flat air boxes and their bikes will hardly run - others get an all round improvement in throttle response and much sweeter running.

So , what is true and undeniable for some folks just doesnt work for others.

I suggest you just try what you want and see what happens.
And if it doesnt work as planned on your bike, try and figure out why - every bike is the sum of its parts and your bike probably has some parts different from other bikes.

Some folks extend the breather hose out to a catch can in behind the battery somewhere, and vent the can through a auto breather filter - from an engineering viewpoint you want as little oil in the combustion chamber as possible anyway.
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Old 02-27-2013, 03:55 AM   #7
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As it is often found with airheads, the devil is in the detail, not all of the Old style airbox covers are the same as they were altered to accommodate revised crankcase breather systems, if you get it wrong you could end up with an airbox that feeds unfiltered air to your engine.

Jim Cray's approach to improving the breathing to flat air boxes is to reduce the length of the snorkels by about 1/2 and cutting 4 x 1.5inch diameter holes in the top of the filter cover. This does require a waterproof air filter element such as a K&N.
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Old 02-28-2013, 03:07 PM   #8
Rob Farmer
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Quote:
Originally Posted by Beemerboff View Post
When Rob Farmer was chasing a mixture problem he fitted a "O2" meter to his RS? which he could read out on the road, and found that the flat filter didnt flow enough at high revs , and stuffed up the mixture.

He fitted a old style round filter which flowed better, and didn't affect the mixture as much at high revs, but it still wasnt perfect.

I spent some time on the Dyno with my PD seeing what worked and didn't work

The flat airbox was spot on for bikes fitted with 32mm carbs but just didn't flow enough air for my 40mm carbed bike.

The problem I had was the lack of main jet sizes for the bings. The early airbox made the mixture too weak at the top end and I couldn't buy main jets in the right size to get it right.I really want to fit a set of Amal mark II carbs before I start messing around again.

What you do appear to get with the early airbox, as long as you have the higher comp pistons, is a much more linear power delivery.

My PD going though it's paces. You can see the early airbox.



I also had it rigged with a air/fuel ratio meter for road testing




This is an interesting read













Rob Farmer screwed with this post 02-28-2013 at 03:14 PM
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