Author Topic: Synchronising Carb Slides  (Read 921 times)

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Online Whitey

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Synchronising Carb Slides
« on: August 16, 2022, 12:19:18 AM »
Just trying to balance the slides on RD250D 1A200 Carbs and I’m struggling to see full circles in the inspection holes if I’m to have any free play in the twist grip.

Best I can get is half a circle at most with only 3mm of free play.

New Gen. Yam throttle cable from either Norbo or Yambits.

Is this norm or should I I be seeing the full circle?

Thanks
Kev


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Offline c50

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Re: Synchronising Carb Slides
« Reply #1 on: August 16, 2022, 08:29:06 AM »
No this is not normal or correct. Your not able to get full throttle. The slides should lift to the top. Something isn’t right, cable or free play incorrect or throttle tube incorrect. Or oil pump cable is incorrect or badly adjusted causing it to hit it’s stop, is the pump cable under the spring retainer and not over it? 

Online Whitey

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Re: Synchronising Carb Slides
« Reply #2 on: August 16, 2022, 08:21:51 PM »
Ok, thanks.

It was a new throttle tube to, again, gen Yam I’m sure… I’ll investigate and report back.


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Offline Cocoablini

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Re: Synchronising Carb Slides
« Reply #3 on: August 16, 2022, 11:27:43 PM »
Make sure your cable from grip to triple splitter isn't bogged down in the front forks too.

Online Whitey

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Re: Synchronising Carb Slides
« Reply #4 on: August 18, 2022, 08:19:39 PM »
Hi all,

Just trying to get to the bottom of this issue….

So, checked oil pump pulley, twist grip tube and cable run… all good.

Popped the slides out and pulled on the cable but can’t get them to the top.

Checked the bag the cable came in - correct part no. On gen yam sticker from Yambits.

Checked the cable for part number and the following is stamped on the outer:

1A01101-1F01

I popped this part no. Into Fowlers website and nothing popped up. The number is printed on the cable about 5cm down from the cable slack adjuster and on the carb cables after the 3 way splitter. There is another number on the oil pump pulley cable which I’ll check in a min.

Has anyone else bought a gen. Yam throttle cable from Yambits or anywhere else recently that could check if they have a number printed on the cable outer and what it is please?

It looks like the wrongs cable in the right bag at the mo but I could well be wrong.

Thanks
Kev


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Offline AndyDean42

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Re: Synchronising Carb Slides
« Reply #5 on: August 18, 2022, 08:59:57 PM »
Hi Kev, I think your issue might be the throttle tube, 5Port reported an issue with new throttle tubes on 14th July not giving full stroke. I fitted a new throttle tube and cable both genuine Yamaha and had no issues on my 400C but there has been a revision to the throttle tube since. Read 5Ports article he explains the differences, if you have your old one you can make the comparison.

Andy
RD400C, RD350B (new project), GS750E

Online Whitey

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Re: Synchronising Carb Slides
« Reply #6 on: August 19, 2022, 12:07:53 AM »
Hi Andy,
I had thought the same as I saw 5Ports post on the throttle tube but, taking the top off the switch gear, I looked where the twist grip would turn to and it was short of the stop. I then detached the cable from the tube, twisted the tube as far as it would go and it rotated another 10mm approx and hit the stop.

To be sure I pulled the cable by hand, not attached to the tube and still couldn’t get the slides to hit the tops.

I thought about it tonight and the only place I can be loosing pull on the slides is in the 3 way cable connector in the throttle cable. If it were a straight through cable I should be able to pull the slides all the way to the carb tops by hand. I have the slides out of the carb bodies btw, to make sure it’s nothing in there stopping them lifting.

I can’t see another place that it could be.

Thanks K


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Offline betty foRD

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Re: Synchronising Carb Slides
« Reply #7 on: August 19, 2022, 02:22:04 AM »
Pretty much leaves your error pointing at the pattern Yambits  throttle cable… it’s not OEM, correct?
I recall others might have had similar problems with fitment.
Rev 'em till they rattle

Online Whitey

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Re: Synchronising Carb Slides
« Reply #8 on: August 19, 2022, 09:01:53 AM »
Pretty much leaves your error pointing at the pattern Yambits  throttle cable… it’s not OEM, correct?
I recall others might have had similar problems with fitment.
Sold as Genuine Yamaha Part - OEM. Cam in bag with Yamaha sticker and correct part number.
Bought from Yambits as Gen. Yam.

That’s why I was asking if anyone had bought a new Gen. Yam. Cable recently as mine has a number printed on the cable outer that isn’t the Yamaha part number. Just wanted to check it hadn’t been mixed up.

I guess there could be a fault in the 3 way splitter which is stopping it traveling the whole way.


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Offline c50

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Re: Synchronising Carb Slides
« Reply #9 on: August 19, 2022, 09:12:43 AM »
Your carb adjusters are well in, my memory of coffin tanks is they are usually much higher than that? Undo the cable from the throttle tube and adjust your carb end to about 1-2mm and see where that puts you. Also if your not getting full throttle your oil pump calibration will be way out. I have bought a few parts in Yamaha bags that have never been anywhere near Yamaha and were unusable junk, all were from India.

Online Whitey

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Re: Synchronising Carb Slides
« Reply #10 on: August 19, 2022, 09:31:20 AM »
Your carb adjusters are well in, my memory of coffin tanks is they are usually much higher than that? Undo the cable from the throttle tube and adjust your carb end to about 1-2mm and see where that puts you. Also if your not getting full throttle your oil pump calibration will be way out. I have bought a few parts in Yamaha bags that have never been anywhere near Yamaha and were unusable junk, all were from India.
I’ll do that. I did just have a similar thought as I was writing to Yambits… I may have been spectacularly dumb.

I’ll re-fit the cable going right back to the beginning and set up the carb ends before fitting either of the other ends and work back from there… I’ll repot back.


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Offline 5port

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Re: Synchronising Carb Slides
« Reply #11 on: August 19, 2022, 10:20:30 AM »

I’ll re-fit the cable going right back to the beginning and set up the carb ends before fitting either of the other ends and work back from there… I’ll repot back.



I think that with this issue you are best to connect it up with the carbs off the bike at one side on a small table/stand and the cable in the air.  This allows you to see exactly how the slides are positioned and that they fully raise and lower.  You can also check if there is a problem with range of movement in the various sections of cable.  You can do this with the oil pump cable connected as well.
As far as the Throttle tube goes, I recently had one that would only give about 23mm of cable travel, that left the slides either too far down or too far up, you need at least 28mm of cable travel, more like 30mm minimum to give a tad of adjustment and free play!
Not absolutely certain of that Throttle tube id, but I thought it was OE, probably 1GU, the superceeded part.  Anyway, the cure for that was to file back the plastic stop bit 10mm, and that gave enough cable travel between the closed stop and the full throttle stop of the tube in its twistgrip casting.
You should be able to find where your problem is by doing the carbs off and connecting it all up.
Cheers

5port
     
5port

Online Whitey

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Re: Synchronising Carb Slides
« Reply #12 on: August 20, 2022, 09:58:04 AM »

I’ll re-fit the cable going right back to the beginning and set up the carb ends before fitting either of the other ends and work back from there… I’ll repot back.



 Anyway, the cure for that was to file back the plastic stop bit 10mm, and that gave enough cable travel between the closed stop and the full throttle stop of the tube in its twistgrip casting.
You should be able to find where your problem is by doing the carbs off and connecting it all up.
Cheers

5port
     

Got that 5port, quick Q, which end stop of the throttle tube did you file back, closed stop or fully open stop?


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Online Whitey

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Re: Synchronising Carb Slides
« Reply #13 on: August 20, 2022, 11:23:12 AM »
Just to report back…

I started again from the beginning and did as suggested with the carbs off and on a table to the side.

Rather than using the dots in the inspection holes, I looked thru the carb bodies to make sure that the slides were fully open.  With that method I can just about get 3mm free play in the twist grip. I’ve had to wind the free play adjuster right in tho, with more force than I would like.

I do wonder if I took a smidge off the throttle tube fully closed stop I could give myself a bit more adjustment room.

Before I get busy with the file does that make sense?

I’m still not sure why it’s tight, I can see no good reason for it. I’m waiting to see what Yambits customer service (who have been very good btw) comes back with after looking at the measurement I took for them, but till then I’ll carry on with the best I can get.


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Offline 5port

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Re: Synchronising Carb Slides
« Reply #14 on: August 20, 2022, 12:04:56 PM »
So, if you measure the amount of cable movement from fully closed to fully open at the twistgrip cable end with the twistgrip cable adjuster fully wound in, what do you get?  It needs to be more than 28mm. However, that is not the end of it, because there is extra for a mm or two of free play and, there is often a slight mismatch of the section lengths of the 3 lower cables, and that has to be possible to correct with the lower adjusters.
Yes, the fully closed stop is the angled one opposite side to the open stop where the round nipple hole is.   I had to adjust mine at the solid angled stop by 10mm because I could not get the slides to quite bottom with all the adjusters fully in, it still left the slide inside edge sticking in about 5mm at WOT.  Cutting back the solid stop gave the extra range of movement I needed.  Your problem may be different.
One thing you can try is connect it up without the twistgrip on at all and see how the carbs set up with you able to pull the nipple by hand.  ;)
Cheers

5port     
« Last Edit: August 20, 2022, 01:39:34 PM by 5port »
5port