Correct throttle cable?

JO55

JO55

Full member
Location
Cornwall
Afternoon all.

In my continued quest to make my Jota even more pleasurable to ride, I decided to fit a new throttle cable. The reason for this was two fold;

1/ I couldn't be sure how long the existing cable had been on the bike, or it's condition.
2/ Last time out, I experienced a slight 'sticking' of the throttle on the overrun. Basically, the revs didn't drop as they should, making braking and downshifting fairly unpleasant.

Given that it's a fairly inexpensive swap, I ordered one up from Ducati Paddy. However, I've gone to fit it this afternoon and the throttle end doesn't fit. The new one from Paddy is a quality Venhill item, but the thread is much larger that the female thread on the housing, and the it appears that the old one also has a free play adjuster that comes with the throttle which is a Tommaselli item.

My question is, which is correct? I suspect that the Tommasselli unit is aftermarket and that the cable supplied by Paddy is for a standard one, but can't be sure. Any assistance would be most welcome.

Also, with the tank and cable off, if I manually rotate the linkage for the throttle, I can feel a resistance 'mid-pull'. Any ideas what this might be (accelerator pump?). It has now made me wonder if this is what is responsible for the revs not dropping off as they should on a closed throttle. I should add that this issue just came on while I was riding, and it's not done it before.

Cheers,

Julian






Jota Throttle cable.jpg

Jota Throttle.jpgJota Throttle 2.jpg
 

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Throttle is Japanese ND, not Tomasselli.
In view of the 3 slide springs, cable is the least likely cause for slides not returning properly.
Suspect dirty or worn slides, damaged needles, bent mounting plate.
Paul
 
As the new cable looks to be correct, one can assume you have an incorrect twist grip... most probably a quick-action item.

To make the ride all the more enjoyable, do yourself a favour and fit an OE throttle, to suit your new cable.

Quick-action twist grips might make sense on a race track, on public roads they're a royal pita imho, especially when there are 3 Dellorto PHB/Fs at the other end. As the revs aren't dropping off imediately, the issue needs to be looked into anyway.

piet
 
Paul Marx said:
Throttle is Japanese ND, not Tomasselli.
In view of the 3 slide springs, cable is the least likely cause for slides not returning properly.
Suspect dirty or worn slides, damaged needles, bent mounting plate.
Paul
Click to expand...
Ah OK. So it should be a ND throttle as standard? That helps, thanks. I get the suggestion of the slides and I'll check it all out, it just seems odd that it should suddenly take effect mid-ride.
 
sfcpiet said:
As the new cable looks to be correct, one can assume you have an incorrect twist grip... most probably a quick-action item.

To make the ride all the more enjoyable, do yourself a favour and fit an OE throttle, to suit your new cable.

Quick-action twist grips might make sense on a race track, on public roads they're a royal pita imho, especially when there are 3 Dellorto PHB/Fs at the other end. As the revs aren't dropping off imediately, the issue needs to be looked into anyway.

piet
Click to expand...
I guess so. The throttle has always seemed rather stiff, but having nothing to compare it to, I'd assumed they were all like that!
 
Julian, do you still have the OEM right switch block in place that's the one with the on/off switch and the starter button? I am thinking you may have had the Tomaselli quick action throttle in addition to the switch block. The Laverda throttle cable screws into the bottom of the switch/throttle block maybe you just need a new throttle tube The Tomaselli certainly would make throttle action stiffer than the already stiff original, ditch the Tomaselli. You certainly need to check the action of the slideS something is not right there. HTH
 
Moisture has an effect on slide return - any chance you were in the rain? As mentioned slide wear is a likely suspect, but sudden changes in operation are not consistent with that. QA throttle a bad idea unless you are able to use softer springs (which can affect slide reurn!). Many on here have also ditched the accel pumps to the benefit of throttle operation and virtually no negative effects on carburation. Up to you.
 
A tiny bit of grease on the accelerator pump grove in the slide helps a lot with smooth application of throttle, found that on my 350 Husky that ran a Delordor carb, it had horribly jerky throttle control just as the pump cut in.
 
78jotadave said:
Julian, do you still have the OEM right switch block in place that's the one with the on/off switch and the starter button? I am thinking you may have had the Tomaselli quick action throttle in addition to the switch block. The Laverda throttle cable screws into the bottom of the switch/throttle block maybe you just need a new throttle tube The Tomaselli certainly would make throttle action stiffer than the already stiff original, ditch the Tomaselli. You certainly need to check the action of the slideS something is not right there. HTH
Click to expand...
Hi Dave,
You may be onto something there. I definitely have the starter and switch cluster on the RH bar. I'll check when I'm next in the garage. Thanks!
 
Vince said:
A tiny bit of grease on the accelerator pump grove in the slide helps a lot with smooth application of throttle, found that on my 350 Husky that ran a Delordor carb, it had horribly jerky throttle control just as the pump cut in.
Click to expand...
Thanks Vince. Makes sense.
 
piranha-bro2 said:
Moisture has an effect on slide return - any chance you were in the rain? As mentioned slide wear is a likely suspect, but sudden changes in operation are not consistent with that. QA throttle a bad idea unless you are able to use softer springs (which can affect slide reurn!). Many on here have also ditched the accel pumps to the benefit of throttle operation and virtually no negative effects on carburation. Up to you.
Click to expand...
Absolutely zero chance of moisture. I've done my time cleaning shiny bikes after a rain ride! I'm getting the picture that the QA throttle is probably not a great idea. Funny, I never even noticed it and just assumed it was a standard fitment.
 
78jotadave said:
Julian, do you still have the OEM right switch block in place that's the one with the on/off switch and the starter button? I am thinking you may have had the Tomaselli quick action throttle in addition to the switch block. The Laverda throttle cable screws into the bottom of the switch/throttle block maybe you just need a new throttle tube The Tomaselli certainly would make throttle action stiffer than the already stiff original, ditch the Tomaselli. You certainly need to check the action of the slideS something is not right there. HTH
Click to expand...
Having now checked, it appear that I did still have the original switch gear on the RH bar. Unfortunately, the throttle part of the switch has been very neatly removed from the casing to make it narrower. Looks like a new throttle it is! Apparently they are the ND item that they fitted to '70's GT two stroke Suzukis.
Also, having removed the intake boots and operated the throttle from the linkage, I can see that it is the accelerator pump that is causing the mid-pull resistance on the throttle. I've put a dab of grease in the actuation grooves, but it doesn't feel much different. I'll investigate further in the winter and give the carbs a proper rebuild I think.
 
Wow, what a difference!! Thanks to Alan, I got my hands on a decent used std throttle. I stripped it and gave it a bit of a refurb and freshen up.
Once fitted with the new cable, the difference is outstanding. An easy, crisp throttle action with a clean snap shut. Totally transformed its action. Thanks Alan for the throttle and everyone else for the advice. Cheers ✊
 
JO55 said:
Wow, what a difference!! Thanks to Alan, I got my hands on a decent used std throttle. I stripped it and gave it a bit of a refurb and freshen up.
Once fitted with the new cable, the difference is outstanding. An easy, crisp throttle action with a clean snap shut. Totally transformed its action. Thanks Alan for the throttle and everyone else for the advice. Cheers ✊
Click to expand...
Stick some lighter slide springs in as well.

Paul
 
ditch the pumps by removing the white plastic bell cranks in each carb (outside then is identical) this removes the "ramp" as the pumps comes in and makes for a lighter action, next, buy the lightest of the three springs availabal (ex Paddy) and clip off 20mm from the length, this I have done and am going to clip another 20mm off, I will only find out when to stop when the slides start to be reluctant to return, but with 20mm gone it is already light, I just think there is more to come, any comment here Haggis, I know you were a clipper in the past, how far did you go?
CLEM
 
CLEMTOG said:
ditch the pumps by removing the white plastic bell cranks in each carb (outside then is identical) this removes the "ramp" as the pumps comes in and makes for a lighter action, next, buy the lightest of the three springs availabal (ex Paddy) and clip off 20mm from the length, this I have done and am going to clip another 20mm off, I will only find out when to stop when the slides start to be reluctant to return, but with 20mm gone it is already light, I just think there is more to come, any comment here Haggis, I know you were a clipper in the past, how far did you go?
CLEM
Click to expand...
I should get around to taking the pump actuator arms out of my 3C. Looking for petrol in deepest France could prove to be stressful.

Paul
 
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