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Carb settings

 
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vort28



Joined: 22 Mar 2010
Posts: 2194
Location: Northwest , UK

PostPosted: Tue Jul 22, 2014 5:11 pm    Post subject: Carb settings Reply with quote

After a bit of a rough run out at the w/e and subsequent investigation I have a few findings.

First one was the cause of the rough running . Having now got 800miles on the vdue it is slowly getting its neck rung a bit harder which resulted in hitting the rev limiter for the first time which resulted in one cylinder going down momentarily Shocked Now up until this moment all had seemed well but afterwards low down running and the following 50 miles home was a chore. Anyway, fairing off, new plug, no difference and still popping out of the front cylinder pipe. Airbox's off and after a complete carb strip and clean of crap out of float bowl but still no improvement. I then noticed the front cylinder slider had a delay before it lifted on the throttle, a quick play with throttle cable revealed that it appeared the cable had been snagged from new and adjusted to suit , and me giving it a handfull had pulled it loose and put the balancing way out. Now readjusted and all ok. I had a look at the throttle cable routing and it is not surprising it had got caught and mis adjusted, so a word of warning to you all. Check the cable for snags and correct seating in carb cap.

I also noticed whilst stripping the cards that I have 220 mains in the rear carb and 225 in the front. Piero's doc's that get delivered with the bikes quote 220/230 ? Anybody know what their bike is running ? And a point of interest, my spare new engine has 220 in both !!!!!
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JRH



Joined: 21 Jan 2013
Posts: 223
Location: West Mids/North East

PostPosted: Tue Jul 22, 2014 5:53 pm    Post subject: Reply with quote

Will check out mine at the weekend.
Just for reference, a TZR250 v twin is 190/260.....
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vort28



Joined: 22 Mar 2010
Posts: 2194
Location: Northwest , UK

PostPosted: Tue Jul 22, 2014 7:06 pm    Post subject: Reply with quote

Thanks JRH, check your cables and carb balance whilst your there as I think anything goes when they leave the factory. Very Happy
Didn't you say users sufers from rough running 4500-6000 also ?
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bimotanige



Joined: 12 Jul 2010
Posts: 582
Location: yorkshire

PostPosted: Tue Jul 22, 2014 11:09 pm    Post subject: Reply with quote

220 and 225 for my carbs mains. cables and splitters are poor fit for sure
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KB1x2, SB3 SB4 BB1 DB2 Vdue Evo YB11 RB1 Ducati MHR Suzi GS650
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vort28



Joined: 22 Mar 2010
Posts: 2194
Location: Northwest , UK

PostPosted: Wed Jul 23, 2014 7:14 am    Post subject: Reply with quote

Thanks Nige, need to order a new emulsion tube as damage one getting it out so had to put a spare in , so thought whilst ordering a new one of those I would get the correct mains also, if mine were wrong that is.
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Matty82



Joined: 10 Jul 2014
Posts: 155

PostPosted: Mon Jun 29, 2015 6:34 pm    Post subject: Reply with quote

Hi
Stripped my bike an carbs just for an inspection (285 miles now)
The plugs are light black but she's still on the running in setting so I'm happy with them.
The main jets are both 220 an the others are 60 an 40 respectively. She runs fine, there is the normal 4500-5500 stutter but that's no prob either.
What is a slight concern though is the right airbox is filling up as I presume the carb over fuels???? Over the course of 80 miles there's nearly a quarter of a pint in there. Any ideas to solve this fellas?
Was a good excuse for a thorough clean though, ha.
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vort28



Joined: 22 Mar 2010
Posts: 2194
Location: Northwest , UK

PostPosted: Mon Jun 29, 2015 6:51 pm    Post subject: Reply with quote

Not had that but I guess your carbs in bits now if you got jet settings, check all jets clear and the issue I had with mine was the choke cable getting stuck on one and the throttle ferrel not being seated properly, so first time I gave it a hand full this seated itself and my carb balance was then way out , so could be a balance issue.
Best I can come up with.
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EYREY1



Joined: 28 Nov 2014
Posts: 113
Location: WAKEFIELD UK

PostPosted: Mon Jun 29, 2015 11:19 pm    Post subject: Reply with quote

is anyone running any different carbs ?
ive got a pair of kehin pwk 39's but not sure about jetting
if i cant get any info i will get it set up on a dyno
running no airboxes as well . i think
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bimotanige



Joined: 12 Jul 2010
Posts: 582
Location: yorkshire

PostPosted: Tue Jun 30, 2015 9:15 pm    Post subject: Reply with quote

Could be a sticking float. Give it all a good clean and check the float bowl fuel levels
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SethG



Joined: 09 Aug 2014
Posts: 95

PostPosted: Wed Jul 01, 2015 12:39 am    Post subject: Reply with quote

I spent a couple of months sorting out the whole carb thing, lots of small pain points. I can summarize here:

1) The Dell'Orto's use a DQ258 sprayer, which limits the main jet size to an effective 206, feel free to fit 220, 250, 350 or 500 size mains, you'll end up with 206. You can run a split configuration between top and bottom, say 220 and 230, or heck even 240 and 250 if you want it richer, or 210 and 220 to lean it out some, the result will be 206/206. If you're running 206 or higher, you're maxed.

2) Take the carb apart and clean it, then weigh both floats, sometimes they get heavy and this will effectively richen the mixture.

3) blow out both vent nozzles on the carb, these often get half jammed with gunk.

4) The carbs use a ram-air system and no fuel pump, this is "sufficient" for a Honda NSR500V, it's sufficient for us, but you have to understand how it works.

The air flowing into the two airboxes is pressurized at high speeds. A carb works by having a known pressure differential between the inlet air which is lower pressure than the float and fuel system, this pulls the fuel up. When you increase the pressure you make it harder for the fuel to flow up, and you will flow less fuel and lean the bike out.

To compensate, both vent lines on the carbs are connected to their respective airboxes, this way the pressure in the intake will equal the pressure in the fuel float and all things will be equal again.

The problem is that this will then resist the fuel flowing in from the tank, lower that quantity and cause the same problem. If you were to add a fuel pump then all would be fixed, because now you've got plenty of fuel flow.

Without the fuel pump, you need to equalize the pressure in the tank to the airbox and the carb. Which is why the tank is sealed and the vent is a hose line running to an airbox. When all three are equal, the bike will maintain constant jetting. When one of these is unpressurized, the bike will lean out at high speeds.

Fuel is overflowing because either the float is sticking, or pressure is holding it open, probably the first.
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Matty82



Joined: 10 Jul 2014
Posts: 155

PostPosted: Wed Jul 01, 2015 10:47 pm    Post subject: Reply with quote

Well, you're not just a pretty face then SethG. Nicely explained, I understood all of that. The only thing is those floats must weigh milligrams each. What weight am I looking at an should they be matched to each other or matched to both carbs?? Will also check the vent pipe from petrol tank to air box
Cheers
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Last edited by Matty82 on Thu Jul 02, 2015 10:48 am; edited 1 time in total
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SethG



Joined: 09 Aug 2014
Posts: 95

PostPosted: Thu Jul 02, 2015 3:34 am    Post subject: Reply with quote

Matty82 wrote:
Well, you're not just a pretty face then SethG. Nicely explained, I in stood all of that. The only thing is those floats must weigh milligrams each. What weight an I looking at an should they be matched to each other or matched to both carbs?? Will also check the vent pipe from petrol tank to air box
Cheers


Ha, no they are grams, clearly noted on the float itself, they sell three versions, 3.6 4.0 and 5.2g, it doesn't take much to move the mixture a bit!
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