Strange Vibration

[adasilva]

Hey Guys.
Back again. This is a continuation of my last post https://foc-u.co.uk/index.php/topic,23866.0.html but decide to open a new one to keeps things neat.


Well after i sorted ou the issue with the TPS and adjusted the throttle cable slack,  the carb cleaning,  bench sync the carbs and changed the oil and coolant i took the back for a ride. (Not a long one i am afraid! :'( :'( )
The bike it starts to shake kind of loosing power or lack of air/fuel i don't know after 4k RPM[/size][size=78%]. if i increase the throttle it goes away a bit and the bike picks up speed but it seems to happen once a change gear and try to increase throttle.[/size]
I read somewhere some guy having the similar issue and it turned out to be a trapped fuel line underneath the tank. I just had a look at the connections and they seem to be fine to me.
i also read somewhere that it might need to adjust the pilot screw so i did that starting from 2 1/2 turns and adjusting to get a better response. That improved a bit but not much.
I am running out of options and at this point a feel that i am going to throw the towel and get the bike to a shop. (Ah!! after all my  work.  >: )


Anyway... if anyone out there had the same or similar issue and can give me some glue on what is or i am doing wrong here i will appreciate.


Thanks guys and girls  :'( [/size]

[darrsi]

Can't see you mentioning the air filter anywhere, have you done anything recently with it?

[adasilva]

Well took it off and clean that was about it.

[darrsi]

Well took it off and clean that was about it.

Clean what, is it a paper one, or a K&N ?

[adasilva]

:lol :lol
I did not wash it with soap and water. Is a paper one. i just used compressed air to clean it.


thanks darrsi

[darrsi]

You can't clean a paper air filter with compressed air, it doesn't work like that unfortunately.
I was gonna say you might have an air leak but if you have a blocked/clogged up air filter then that will cause issues too.
And you can't tell if it's blocked by looking at it either, unless it really is filthy.
With all the work you've done i'm surprised you haven't changed it anyway just to eliminate it.


The thing is, if you do a carb balance with a clogged up air filter then you get a false reading, so the carbs will be adjusted wrongly making the bike run badly when you get it on the road. I've done it myself before but with a cheap air filter that wasn't letting enough air through, i changed it a few days after fitting and had to do the balance again, then everything was fine.
Although i did replace it with a K&N which does have much more airflow (and you can clean them with detergent and water).


I'm not saying this is your problem, but it is something that i would certainly consider changing, just to tick it off the list, plus if you don't know the history of the air filter then it won't hurt anyway.

[adasilva]

Thanks darrsi for you reply.
That was bit fool of me doing everything and did not change the filter. I will get a new one any way even if that turns out not to be the issue. I don't know when the last owner changed this thing and by the looks of it is been a while.
i will let you know.
Cheers

[darrsi]

As was brought to my attention on here, we can get some weird and not so wonderful weather that can consist of smoke or even desert dust from abroad that can really mess with an air filter, especially if the air has been damp beforehand.


Totally up to you but consider a K&N air filter, they're a little bit dearer than a paper one but it"ll be the last one you ever buy for the bike.
They're pretty low maintenance, but when i do clean mine i use washing machine powder in warm water and just shake the filter gently in the water for about 15mins, then rinse off with plain water and let dry naturally. I do a light spray of the proper K&N air filter oil afterwards though.
It does make the throttle response sharper and you just get a cleaner all round feel when accelerating.

[Disorderlypunk]

ive suffered the bad vibrations and i found this fixed it
https://youtu.be/Eab_beh07HU?t=25s

[Adam2201]

ive suffered the bad vibrations and i found this fixed it
https://youtu.be/Eab_beh07HU?t=25s

This was a risky click at work!

[His Dudeness]

Did this problem only start after you worked on the carb or was it there before? Between fully open and fully closed what throttle position are you having the problem? From what I picked up the problem is at low throttle input and things get better as you open the throttle wider. Is that right? That would suggest to me a problem with pilot jets, mixture screws. At small throttle inputs they make a large contribution but as you open the throttle they have less influence and the main jet and needle contributes more so if it's a problem at small throttle input I'd guess blocked pilot jets, mixture screws not right. A quick test you could do that would help confirm that would be to richen the mixture by giving the bike a bit of choke and see if that improves the problem. If it does then you have a weak mixture. Another trick to help pinpoint the problem is to throw water on your headers after a test ride and check to see if they dry at the different rates. A lean cylinder will be hotter so should dry quicker than the others. Your mixture screws should be close to the factory spec they shouldn't need much adjustment if the do then something is wrong.

There's a graph of throttle position vs what part of the carb is having an effect http://www.ducatitech.com/2v/img/fcr_graphs.gif

[adasilva]

Hi there.
This problem only started after i cleaned the cabs. The problem occurs when lets say i am on 5 gear and slow down and switch to 4 and after that try to pick up speed. I guess fully closed to fully opened.
Correct. When i open the throttle wider it stops and pick up speed.
I think block pilot jets might be out of question since i cleaned the carbs. I think it might be the mixture screws.
The mixture screws factory spec as per manual is 2 turns out. At the moment they are 2 1/2. Should they all have the same turns?


But my question is if the issue is the mixture screws how do i set these to correct this problem?


I will do the test that you suggested and see.
I will let you know


Thanks for you info.

[His Dudeness]

If the problem wasn't there before and now it is it has to be something you've done so back track on everything you've done. I don't think 1/2 a turn on the mixture would cause your problem. I think it's more likely that something isn't right in the carb. Try a bit of choke and see if it improves the symptoms. That'll give you some direction

[redmandan]

I'm doing a carb rebuild as well. Last time I had my carbs out I put all the pilot screws back in with the same amount of turns they had out, each carb had between 3.5 and 4 so that was quite a lot. I decided to put them back to factory after doing a bit of reading around even though somebody must have set them like that for a reason. My bike never requires choke to start, which suggests it's running too rich.


Sorry your first outing wasn't perfect, hope you get it sorted.

[adasilva]

Ok. I have ordered a new air filter and reset the mixture screws to factory default.
Waiting on delivery of filter to try it out.
Will let you guys know.


Thanks

[His Dudeness]

Did you try riding it with a bit of choke? Did it make it run worse or better? You're using the choke to try and figure out if it's running too rich or too lean. That will tell you where the problem is. If you want to test if the old air filter is the problem just take it out and go for a short spin to see if there's an improvement. If there is then the filter is blocked. I'd be surprised if it was the filter just because it was ok before you did the carb work right? So it should still be ok unless you blocked it somehow. 1/2 a turn on one mixture screw wouldn't be enough to cause a big problem. They're an adjustment point they don't have to be exactly at 2 1/2

[adasilva]

Hi
I did not get the chance to do a test as the weather here was crap this weekend.
I don't think is the filter as i did not have this problem before the carb work. but since the inlet rubbers were cracked and i changed them, there is a possibility that there is less air going in now and the filter is the only thing i did not do.
i will try your suggestion as soon as I can and let you know.
thanks

[adasilva]

Did you try riding it with a bit of choke? Did it make it run worse or better? You're using the choke to try and figure out if it's running too rich or too lean. That will tell you where the problem is. If you want to test if the old air filter is the problem just take it out and go for a short spin to see if there's an improvement. If there is then the filter is blocked. I'd be surprised if it was the filter just because it was ok before you did the carb work right? So it should still be ok unless you blocked it somehow. 1/2 a turn on one mixture screw wouldn't be enough to cause a big problem. They're an adjustment point they don't have to be exactly at 2 1/2

Ok took the bike for a ride yesterday.
I tried to ride it with a bit of choke and it seems worse than before. So i presume is running too rich. Am I correct in saying that? Strange enough is that this happens only when going from low gear and increasing the throttle. Let say if i am in 4 and changed to 3 gear and slow down, when i try to pick up speed if i open the throttle half way quick the issue happens but if i don't open the throttle half way but steady increase it then it is fine.


I am expecting the new filter tomorrow so i will test that as well.


thanks

[Disorderlypunk]

ok so going through everything im going to start with your cracked carbs
were they cracked all the way through or just the outside?
all should make sense if they were through and were leaking  UNfiltered air in and the previous owner has increased the pilot screws to let more fuel through to richen up the lean conditions caused by leaking inlets (we good so far)


if there is now no UNfiltered air going in the inlets anymore it draws it through carbs so increases the negative pressure/flow rate in the carbs and in turn the airbox which means more air is needed to flow through the air filter than previously, so a blocked air filter may be to blame here (and would actually make the UNfiltered air coming through the old inlets even worse)


so a combination of things will be causing you issues here
you have already replaced inlets -should only be filtered air now
1. running rich as pilot screws are allowing too much fuel to flow screw them back in a bit to factory
2. air flow is restricted causing a negative pressure which sucks up more fuel making run even richer - pull air filter and replace (worth doing anyhow)


this is just the things that are popping into my head as i read all the problems that you are systematically going through which is the best way

[Disorderlypunk]

ooh and you didnt move the clips on the needle when you were stripping the carbs did you ?