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Old 08-31-2012, 01:05 PM   #1
clfhngr OP
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r80 g/s throttle

hi,
any suggestions to smooth out throttle roll on/roll off on 81 r80 g/s. have stock bings, replaced cables, checked routing and have ez pull springs, but roll off on throttle still not very smooth. very annoying when slowing into corners on twisties....

not sure if this is related to carbs (should i switch to mikunis), cable setup or....?

suggestions?

thanks
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Old 08-31-2012, 01:28 PM   #2
mark1305
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If the G/S has the same bevel gear setup as my ST, check under the top plate on the twist grip body to see if the gear teeth on the quadrant and/or the twist tube are worn beyond use. Maybe a cleanup and fresh lube inside the twist tube and on the gear teeth will cure the probs.

If you have never opened that part up before, note how everything lines up before the parts jump away from each other. Putting it back together isn't hard - you just have to have a little manual dexterity to keep the teeth meshed properly for full range of throttle action while putting the stuff back together and getting the top cap back on to hold it in place.
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Old 09-01-2012, 08:11 AM   #3
batoutoflahonda
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also, with the bike off, open the throttle wide open and let go. it should return to full close on it's own. In reality, it should snap back, but at worst it should close at a pretty a good rate. then check to see on the carbs if they have returned to their idle stops. if both haven't, or are very slow then do as the previous poster mentioned and check routing. if slow and one has but the other hasn't, check for routing and on the carb that hasn't returned to the stops or is slow to do so, try cleaning around the shaft where it passes into the carbs. then lube with silicone grease. Maybe best to tilt the carb to allow the grease to penetrate. Some times they get gummed up or really dry down there and stick a bit.
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Old 09-01-2012, 08:27 AM   #4
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Ditto on the cam gear and throttle tube teeth being worn.
You can get a new cam gear and throttle tube pretty cheaply- hopefully the actual throttle assembly where the cam gear rides isn't worn out, as that is a bit more expensive to replace. Worth checking out.
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Old 09-01-2012, 09:39 AM   #5
Rob Farmer
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31.50 or whatever it is in your funny money ($50?) for a new throttle cam and twist grip (includes a new rubber grip) --> under handlebar and lever assemblies http://www.motobins.co.uk/bmw-parts....20valve%20Twin

a lot cheaper than fitting mikuni's (you'll need the twist grip and cam anyway)
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Old 09-02-2012, 05:44 AM   #6
clfhngr OP
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Thanks for suggestions. The cam was pretty gnarly, so will give that a shot first. Cable snap back seems pretty smooth.

Cheers
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Old 08-11-2014, 11:22 PM   #7
_cy_
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what's the best place to get a new throttle cam and twist grip for 81 R80G/S ... single-pull with hydraulic MC?
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Old 08-11-2014, 11:41 PM   #8
Rucksta
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If you are replacing the twist grip and crown wheel, spring for a new top cap as well.
Wear on the pivot is harder to detect yet it will accelerate wear on the other two components.

Later model bikes have a large diameter centre boss.
These wear much better than the earlier smaller type and the related crown wheel seems easier to source.


P.S. the twist grip and crown wheel have alignment marks that are easy to miss under a layer of lubricant.
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Old 08-12-2014, 12:00 AM   #9
_cy_
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got the earlier smaller type stepped crown gear .. no problems with alignment. mine are hosed ...
just found part numbers on Bobs BMW ..

what's the best source for throttle handle assembly and crown gear?

#6 and 10 needed

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Old 08-12-2014, 07:06 AM   #10
Bill Harris
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Quote:
Originally Posted by Rucksta View Post
If you are replacing the twist grip and crown wheel, spring for a new top cap as well.
Wear on the pivot is harder to detect yet it will accelerate wear on the other two components...

...P.S. the twist grip and crown wheel have alignment marks that are easy to miss under a layer of lubricant.
On the /5's, earlier bikes (and some later) have a top cover that measures some 77mm in length but the current (and only) replacement cover measures 89mm. Won't fit.



The alternative is to get a new right grip assy, and at $200 it doesn't even have the correct patina!!!! If yours is very worn, you may be able to get the clearances OK with very careful lapping.

One thing I do on my throttle tube/throttle cam is accentuate the alignment marks by making a larger dimple with a 3/32" drill bit. Helps when you're up to your elbows in Lithium grease and fighting springs and/or twangy cables to get the throttle assembled...

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Old 08-12-2014, 09:22 AM   #11
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According to Max BMW the only cam available is the later 15mm pivot style and must be used with the newer cover. If you have the early cover with 8mm pivot you will have to replace both cover and cam. Around $80 for everything.
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Old 08-12-2014, 11:31 AM   #12
_cy_
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logic says a throttle assembly with a 33 mm cam, double pull should work fine with a single cable. this would allow more choices finding a used throttle assembly, which are dirt cheap on ebay.

has anyone actually used a double pull complete throttle assembly with a single cable system?
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