Date: 17-08-22  Time: 23:21 pm

Author Topic: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING  (Read 1374 times)

TOM VR46

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Soz , its a bit late but ive been doing a lot of head scratching  :z .
Ive just spent 3 days putting a new cam chain in,, around 75000 on old one so new one needed. No adjustment left on tensioner.  :'(
All seemed ok. Running in shed ,, didnt rev to much in shed as i wanted all engine parts to settle and oil to flow round.
Then off for wee run.
Out of drive and i noticed shutting off throttle and the revs were'nt dropping too quick. Not sticking open , just coming down slowly. :rolleyes
Just a short run and still the same at the end.
But i never touched the carbs,,, just took them off,,, and put them back on. Yep cables were off but when i put them on i checked the throttle and it was'nt sticking just usual nice spring back when you let go.  And again after run ,, throttle just snaps back but revs come down slow.
 
any ideas, cause i confuzzed :o




Gnasher

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #1 on: 03 May 2022, 09:38:05 am »
The likely cause is an air leak, from the carb rubbers.  They may not be seated properly around the carbs.  Check the 2 inner ones these can deform while refitting the carbs and you only need a slight leak.  Also check the balancing port caps are fully seated and not split.   
« Last Edit: 03 May 2022, 06:11:00 pm by Gnasher »
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TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #2 on: 03 May 2022, 07:27:30 pm »
Yep Gnasher the two inner rubbers are a pain to get on.
YEP ..definitely air getting in. Had a small amount of brake cleaner in an aerosol and sprayed it around carbs and revs went up.
Now the weird bit  :\ . Put wee red extension pipe on spray so i could spray a bit more closer to each rubber,,, no real increase there. This was both rubbers on each carb. Then for no reason i sprayed over the top of each,,,,,  on the left carbs 1 & 2 no change.  On carb 4 small change.,,, Now carb 3 revs shot up  :eek .  So im still confuzzed but closer to problem but cant see what or why .


So why would i get air coming in from the top when again carbs were not touched. 
Well im part way there but will have to wait till weekend now.  Work always gets in the way.
Any ideas of why im getting result spraying more over the card extremely welcome.

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #3 on: 07 May 2022, 10:20:31 pm »
Well im no further forward with problem :rolleyes .  Circlip on carb 3 wasnt too tight, gave it about a quarter turn. Apart from that couldnt find any air leak . So decided to put carb tune on and see what that showed.  To be honest they werent too bad. Carb 1 was about the most out but not by much.
So tried another wee run and just the same, shut throttle and it runs on.
Now ive been doing a but of thinking and yep i may have small air leak somewhere, but is this possible,,,
when lining up timing marks when putting head together which were right just before final tightening and torque ,,, have i just knocked it off slightly.
The reason im now thinking this is im sure i read someone putting head back on and when tightening down cams the two small end dot you line up moved off slightly,,, but i cant find the post to see his problem.
Im sure i didnt move the alternator off its mark,, but now begining to question it. 
If ive knocked timing off would it cause bike to not throttle down properly.   Any ideas.
Oh on short run i did open throttle a bit, and just as i thought it didnt want to pull , i wasnt expecting it too but just opened to see what would happen.

Gnasher

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #4 on: 08 May 2022, 06:32:30 am »
Incorrect valve timing will not give you the symptoms your saying the bike has.  Providing everything is working as it should, ie its starting, idling, pulling etc, slow at losing revs, it's an fuel/air problem. 

Take the carbs back off and check them over.  It's possible you've disturbed, damaged something.  Also recheck the pull/push throttle adjustment, incorrectly set can give you the very same symptoms.   



 
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TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #5 on: 08 May 2022, 09:18:39 am »
Ok.  Here we go again. Ill take of carbs and check them over again. And check throttle push/pull as i take them of just incase something there.
And strong coffee first,,, might help. :)

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #6 on: 14 May 2022, 08:58:41 pm »
 :rolleyes  Well im still in limbo. Went back to start. all off. Timing was out and this was my mistake. When i put cams back in and lined up timing marks i hadnt noticed it had moved at alternator mark. I had just watched dots staying lined up on cams. Then turned over with hand afew times but didnt recheck timing marks. Both were 1 tooth out. So reset cams and yes checked timing marks and rechecked , twice all good.
So thought this would help ,,,, nope :'(
Ive checked carbs but have not pulled them apart as i never touched them to start with. Sliders are all ok and come down with the usual woosh sound. Flaps spring back and cables on in right order. Flick throttle and all good. Carbs back on and balanced all good. Checked TPS and sitting at 5..
Bike running and because im in shed give it a wee bit throttle and all seems good. Or as good as it used to be.
So test run. and few yards up road , first junction . and revs not falling quick enough. Slightly better but not right. If stop revs are still falling when im stationary.  Its not like cruise control,, as when i take speed up and just let throttle go it will slow down but far too slow . The last say 1000 down to tick over seem the slowest. Tick over is 1100 ,, this is slightly up from what i used to have. It was around 1000 but not above.
Ive had carbs of again :o  and again all seems ok. I did reset mixture screws to 2 turns out,,, just to see,,, and no difference.
Im stuck for ideas.

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #7 on: 15 May 2022, 09:32:16 am »
Still sounds like either an air leak or a kinked breather hose

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #8 on: 15 May 2022, 11:27:17 am »
Yep. Going to have another look over and hope to see something.
Had a look through internet last night and seems this can happen to all makes and models. One i read was more or less exactely what i said in first post.
So its a case of crossed fingers and hope something crops up. :)

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #9 on: 20 May 2022, 05:36:15 am »
 :'( Well think ive lost the plot.  After not finding anything obvious i decided last couple of days to take bike to work. On wendesday , whatever i did i got the bike to start dropping revs to point it was only last 1000 or so that would be slow , so thought not too bad so off to work.
Half way to work stopped at shop,, went restart bike and tick over was about 2000 ,, i sat for a few mins to see if they would drop but stayed up so i lowered them back to 1100.
At work stopped and again revs stuck at 2000 :rolleyes ,, sat for a bit but again didnt drop so i lowered them again..
So thats now twice ive lowered the revs to achieve 1100 tick over,, why isnt it just not cutting out,, pass.
After shift started the bike and was expecting it not to tick over but it did. So off home. Home and still ok.
Today once again got to work and had to lower revs,, im now not getting this at all. But to add to it a simple thing , seal gone on rear brake :o :o .
After shift started bike and guess what,,,, it wouldnt tick over and after about 15mins trying to set it i gave up and came home with a few bump starts,
so im lost .
When i got the bike i had broken spark plug which was head of fix , back together and ran straight away.
Broken exhaust stud , again strip to fix, back together and ran straight away.
I never expected this so dont know what to do next.

Gnasher

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #10 on: 20 May 2022, 07:55:34 am »
Mate I've given you all the likely possibilities, either you're missing or you've not installed or set something correctly.

The only other possibility is the carbs, I know you said you didn't touch them but it could be just coincidental.  Check for bent needles, partially or blocked emulsion tubes, damaged or leaking metering valves, damaged or sticking throttle valves, lose/bent/damaged butterfly valves, brittle/holed/cracked diaphragms, broken/damaged diaphragm spring I've seen these cut down in the past, partially blocked air bleed passages and general condition or the carbs.  Something as simple as oxidation (white powder) in/on any part or the body where a slide/valve has to move past or fuel/air has to pass through will have an effect.           
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TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #11 on: 21 May 2022, 03:02:42 am »
Thanks Gnasher.  Will give it another going over and take time with it. Just stumped with whats gone wrong. And ever time i start it something different happens. Didnt take out today , but started it and it did,,, and just sat and ticked over.
But ive got the patience just need the time and ill get there.

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #12 on: 21 May 2022, 10:38:38 am »
Had the same issue on my Serow Had the Carb apart and everything was fine. I check the diaphragm and found it was not very flexible. Luckily it takes the same diaphragm as the FZS600, swapped the diaphragm from a spare set of carbs I have and has been perfect since. . Only ever came across the issue in an old CB250K2 back in the 70s.

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #13 on: 22 May 2022, 10:59:54 am »
hi bud if your clutch plates are binding that will cause exactly that the revs will match the revs of the engine so its time to sort out your clutch plates also the carb rubbers are another so both are a idea to sort out

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #14 on: 23 May 2022, 12:22:25 pm »
Thanks for replies and ideas on this. Due to waiting on brake seals im taking my time.
Carb port caps,, possible small hole in one but you have to blow dam hard ,, so idea for this is when i get round to starting her up again ill put heat shrink over and bend last 5mm or so over and then cap.
Possible carb 4 slider making different noise when just flicking them up and letting drop ,, but just slight difference. Havent taken apart yet just visual check.  Butterflies look ok open and shut ok . No difference using throttle to open and shut.
I did recently put new clutch plates in but to be honest didnt like them so old ones werent slipping or anything , just age so put them back in and keep new for spares if needed.
Carb rubbers to head all good as these arent to old, no cracks or splits.
So time for new carb cleaner and will take time and have a wee look inside. And clean the glasses first too :D :D .


unfazed

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #15 on: 24 May 2022, 12:10:16 am »
A small dab of superglue on the hole will sort it for now.
Worked for me years ago on an XJ500, when I could not get diaphragms for a month, but need ed the bike for work.
It worked so well I never bought the new diaphragms and sold the bike over 3 years later and they were still perfect.

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #16 on: 25 May 2022, 04:39:52 pm »

Possible carb 4 slider making different noise when just flicking them up and letting drop ,, but just slight difference. Havent taken apart yet just visual check. 


Whip the top off and check the diaphragm

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #17 on: 28 May 2022, 10:27:34 pm »
Well. Carbs cleaned and one wee small dab of glue on a spot on diaphram 4. Didnt flex it too much but gave it close look.
Everything else looked ok on 4 so all back together and,,,,,, :) :rolleyes :)  so far so good. Tick over looks good and revs falling in time with throttle.  :)
So test run tomorrow and looking forward to it.
I took two small vids to show tick over and revs , but took them on my phone and cant get them to load. Says file size too big, but there only short vids. And my phone will not connect to this laptop.  Will try to get them on , somehow.
But after afew weeks of head scratching ,, getting there,, hopefully.
Big thanks to all support. Now tomorrow.

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #18 on: 29 May 2022, 11:36:40 pm »
I may give vids one more attempt , one at a time. There short so should have posted.
Wee test run today all good. Happy Fazer  :) .
Thanks again.

TOM VR46

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #19 on: 29 May 2022, 11:38:39 pm »
One posted, try two.

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Re: THROTTLE OFF, REVS GOING DOWN SLOWLY. BUT THROTTLE NOT STICKING
« Reply #20 on: 30 May 2022, 08:00:55 am »
Looks like it's sorted,  :thumbup
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