Carb question

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r75bitsa
Posts: 58
Joined: Wed Jan 30, 2013 8:49 pm

Carb question

Post by r75bitsa »

G'day
Finally have the rocket going and all in one piece. Now tidying up all of the fiddle bits you leave behind just to get it fired up. I seem to have a problem with mismatched carbs. The bike started out as a 73 R75, then due to storage issues from the previous owner, it would have required a complete rebuild to bring it up to scratch engine wise. So a78 r100 motor was sourced plus wiring loom tank and seat. Many years later it's a goer and I've a suspicion that the bloke I got the carbies from might have been telling porkies. He said no worries mate these suit a 78 r100.
The right hand side is a 64/32/306 from an 83-86 r80gs and the left side is a 64/32/347 from an r65ls. Yeah they look the same. They appear to have the same main and idle jets as an 81- 84 r1007. The r65 carb has the different needle arrangement, the r80 carb has the push and turn adjustment method along with no jet arrangement in the corner of the bowl that the r65 has. Only a brass fitting with a hole which I imagine is the same as the jet measurement. :idea: I know there are different mixture settings and whilst the bike idles ok,which after so many years you are tempted to ignore until it really pisses you off, is this a situation that won't take too much to fix. Rather than scratch around for suitable carbs.
r75bitsa
Posts: 58
Joined: Wed Jan 30, 2013 8:49 pm

Re: Carb question

Post by r75bitsa »

The right hand side is quite obviously burning more fuel.
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SteveD
Posts: 4839
Joined: Tue Aug 03, 2010 3:29 am
Location: Melbourne, Oz.

Re: Carb question

Post by SteveD »

64/32/306 is actually listed as a R80 carb not an 83-86 r80gs.Similar though.
Slide 906-1, MJ 145, needle jet 2.64, jet needle 241, atomiser 591, idle jet 45, throttle valve and shaft 850/433, clip pos 4, float bowl 60, idle mix setting 0.5

64/32/347 is actually listed as a R65 carb, not r65ls. They're almost identical though.
Slide 907-1, MJ 138, needle jet 2.64, jet needle 241, atomiser 591, idle jet 45, throttle valve and shaft 850/433, clip pos 3, float bowl 66, idle mix setting 0.5

A starting point would be MJ's and clip positions the same. I'm presuming you've done that?

Are you comparing the R100 32 mm flat tops or the 40mm versions?

When you're close to happy, if you want to try out the harmoniser carb tuner, let me know.
Cheers, Steve
Victoria, S.E.Oz.


1982 R100RSR100RS supergallery. https://boxerboy81.smugmug.com/R100RS
2006 K1200R.
1994 R1100GS.
r75bitsa
Posts: 58
Joined: Wed Jan 30, 2013 8:49 pm

Re: Carb question

Post by r75bitsa »

I have no experience with cv's mate most bikes in the past I've owned have been ducati, so pumpers, even though I've cleaned them up and got them running I'm at sea as to sizes relative to models. The mj is 160 and idle jet is 45, what sizes are relevant to this motor.The info I looked up was from the clymer for the r100/7 for the jet sizes and they are for the 32 mil.The slide and needle setup are different from each other, I'm wondering if that is going to be in the too hard basket. Thanks for your information Steve. I notice that the slides are different numbers as are the float bowl jets, though the r80 carb is missing the jet in the bowl. Will it be possible to get them working as they should or will I have to start again, I have had limited exposure to the style of carb even though they are fairly easy to strip and assemble.
Regards to everyone.
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SteveD
Posts: 4839
Joined: Tue Aug 03, 2010 3:29 am
Location: Melbourne, Oz.

Re: Carb question

Post by SteveD »

If it's starting and idling then I'd be inclined to try and sort them to be at least similar in jets etc. The bowl jet is a cold start jet and allows fuel up into the aux carb (choke) If it's starting ok then maybe that doesn't matter?

They're simple to use. If I can almost do them then anyone can.

This is close enough to a Bing..
.https://youtu.be/IBFq9nHVmks
Cheers, Steve
Victoria, S.E.Oz.


1982 R100RSR100RS supergallery. https://boxerboy81.smugmug.com/R100RS
2006 K1200R.
1994 R1100GS.
r75bitsa
Posts: 58
Joined: Wed Jan 30, 2013 8:49 pm

Re: Carb question

Post by r75bitsa »

Both carbs have a 160 main and a 45 idle jet, would you go down to the r80 setting or persevere with the current setup. Apart from the difference in the slides and the ? Missing jet in the r80 bowl they are pretty near the same.
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SteveD
Posts: 4839
Joined: Tue Aug 03, 2010 3:29 am
Location: Melbourne, Oz.

Re: Carb question

Post by SteveD »

I think I'd head towards the R100 setup. The 160 MJ would work fine in a 40mm Bing.
I'm unsure if it's needed in a 32mm carb. A previous poster to this forum, a self confessed mastertuner, was adamant these bikes worked best when more lean then rich. MJ's are cheap to buy. It might be worth getting 150 and 155's to play with?
Cheers, Steve
Victoria, S.E.Oz.


1982 R100RSR100RS supergallery. https://boxerboy81.smugmug.com/R100RS
2006 K1200R.
1994 R1100GS.
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