Slack in throttle

[hudson]

Hey guys. I’m having trouble with slack in my throttle on my r75/5. Installing new cables, taking all slack out. I made sure the teeth markings on the cam throttle grip matches the throttle twist grip teeth, and the square ball end holder sits correctly in its position in the channel of the housing . The carb slides don’t start rising until the throttle is half way turned. The teeth don’t necessarily feel like they are slipping when twisting but maybe????

Can the cam gear be readjusted so markings don’t match the throttle teeth? If adjusted like this I guess the cam chain will be too short, so the throttle cable play won’t be be able to properly rise the carb slides? Or maybe it won’t allow the housing cover to close?

This is the original cam and throttle and it is set properly as described- will replacing with new cam & throttle necessarily fix this? I’m sure it can’t hurt but I want to know if this is the source of the trouble? Or if I should look at other causes first.

Thanks!

[Zombie Master]

If the old cables are the same as the new ones, then you may have to experiment with the position of the cam gear. They can be confusing to set up.

[Rob Frankham]

You should try to look for other reasons for the problem before replacing expensive parts.

Twist grip gears do wear and slip but what they don't do is go back to normal when the throttle is closed so it should be immediately obvious what has happened because the index line on the gears won't be indexed any more. In any case, it will only happen if the gears are severely and obviously worn which should be easily visible. You will also have been suffering from a very notchy throttle action for some time.

I'm a bit confused by your description. You suggest that you have taken the slack out of the cables but that the throttles still don't start to open until the twist grip has turned through half it's movement. I don't really see how this can happen. If there's no slack in the cables, the throttles must start to open immediately. Late opening of the type you desctipe must mean that there is a significant amount of slack... probably at least half an inch.

If the throttles aren't opening until the twist grip has been turned halfway, they will not open fully and you'l lose the top end of the throttle... important mainly for acceleration... so this is something that does need to be sorted out.

If you deliberately misalign the gears to take up the slack, then the grip will hit it's stop before the throttles are fully open.. as bad scalded as burned...

As I see it, there are three possibilities:

1. That the gears are so worn that they aren't engaging until the grip has gone halfway... I think you'd know if this was the case but...
   
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2. The cables are 'hanging up' so that you aren't getting rid of all of the slack when you adjust or...
   
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3. The new cables are wrong and have too much slack built in (although why you don't notice this when adjusting, I can't say).

I think I would dismantle the twist grip completely and closely examin it for wear or damage. Compare the new cables with the old to ensure they are the same spec then reassemble very carefully making absolutely sure that you have identified the indexing marks on the two gears correctly and that they are properly aligned.

Rob

[hudson]

Thanks for the input, I don’t have the old throttle cables. I bought new ones a while ago from Rocky Point since I have Mikuni carbs. I’ve been riding my other beemer during the summer so I am just getting around to this plus regular maintenance on the /5.

After I installed the new cables I took all of the slack out - turning adjustments all the way out until they are practically disconnected. Don’t know another way unless I am missing something.

As I stated, the throttle markings are matched so I guess the only recourse is to play around with the throttle? If I force the throttle further on purpose it will slip in the teeth, but not by normal turns. It seems though that is the market match up this would not make a difference in replacing the throttle unit, matching the marks up the same.

I will also measure and get with Stan to make sure I have the correct length.

Let me do a little more experimenting and I will get back.