Rejetted, and WORKS! now running rich in low revs?? - SV650.org

16-03-06, 02:02 PM

Following on from my adventures here, here and here:

I've put everything back togethere, with the new 145 Mikunis and moved the clip up one notch on the needle (so there are now two free notches below it, away from the point).

Fantastically, the bike started. I had to run it on the starter for about 30 secs, but I presume that's because there was no fuel in the carbs? Anyone confirm?

It runs fine now.

But at around 2-4k RPM, the revs don't back off normally when I close the throttle; there's a small delay. I resume this means it's running a bit rich? Everywhere else is fine.

This can;t be the jets can it, since the jets mainly affect the upper revs? Any ideas why this might be? I did readjust the mixture scres 2.5 turns from where it just seats. I've also made sure the idle ias around 1300 RPM.

Any tips (Northwind?)

16-03-06, 02:06 PM

Are all cables and linkages free and lubed?

16-03-06, 02:08 PM

Bit naughty, ut I didn't actually lube anything. But it only happens at low revs, so that shouldn't be the cause. What's recommended for lubing the throttle cables and stuff anyway?

Thanks.

NedSVS · 16-03-06, 08:07 PM

Yes it is normal normal to take a few seconds more cranking when the float bowls have been emptied (but perhaps not as much as 30 seconds). Your revs hovering at 2 - 4k is usually an indicator of the air pilot mixture being lean (the increase in main jet size will only have had a very small effect on the low speed running). First I'd try turning the pilot air screws out to 3 1/2 turns out and see if that helps. You may well find you need larger pilot jets with your de-baffled CCC. If you do, you can get them from Allens R&D in Nottingham (01949836733) part number N224.103 follwed by the number of the size you want (17.5 is standard, so you want 20.0 or 22.5). Hope this is of help.

northwind · 16-03-06, 08:12 PM

I doubt that... 3.5's a lot, I'm running a full system, better filter, and tank spacers and I'm on 2 3/4. He's not changed the induction at all since before the rejet and it ran normally before.

There's a chance you have a problem with the choke cables- did you remove them at the carb end? They can stick there, and the cables can get stuck in teh wrong position at the ends and at the y-splitter (sleeve pulls out of the mounting sometimes.

NedSVS · 16-03-06, 08:25 PM

Northwind wrote:

Quote:

I doubt that... 3.5's a lot, I'm running a full system, better filter, and tank spacers and I'm on 2 3/4. He's not changed the induction at all since before the rejet and it ran normally before.

This just shows how much variation there is from exhaust system to system. I beleive you (Northwind) run a BMC RS filter like me, but with my micron/Quill hybrid I am running 22.5 pilots at 2 1/4 turns out. I could get it to run on standard pilots but always had a tiny flat spot just off closed throttle. I don't beleive I have any air leaks (I put everything back to my known stage one induction settings to check this).

northwind · 16-03-06, 08:58 PM

What I mean is, I doubt it's his problem. Different systems call for differen thtings, you're right- the restrictive headers of the Micron systems fuel better low down while a more open system like mine gives more top end... But he's got a standard system.

NedSVS · 16-03-06, 09:21 PM

Northwind wrote:

Quote:

But he's got a standard system.

Not quite true, I'm sure the CCC will have some effect too, not just the headers. I'll be very interested to know the result of this one; so let us know how you get on

16-03-06, 10:58 PM

Following on from Northwinds point on the choke cable. Mine has been running very rich. So rich that you can smell the stink of petrol coming out of the exhaust.

The choke cable was working fine. I have now stripped the the carbs off again and found that the front choke plunger had seized in the open position. This caused the front cylinder to run rich constantly, regardless of the choke position or indeed the operation of the choke cable itself.

When I finally got the crappy cheese bolt undone on the front plunger and pulled it out, it was actually rusted in position.

Having now sorted this problem the bike runs a lot smoother in the lower rev range.

I do however need to replace the choke cable, but seeing as I never use it anyway, it can wait.

northwind · 16-03-06, 10:59 PM

Marginal though. Certainly not enough to have this huge impact on the idle circuit. And not when it wasn't an issue before he rejetted. This is something new that's happened as a result of the breakdown and/or rejet, and since everything else he's done is to richen things up, why would he now be dramatically lean at idle?

I bet you 10p

16-03-06, 02:02 PM	#1
Saracen Guest Posts: n/a	Rejetted, and WORKS! now running rich in low revs?? Following on from my adventures here, here and here: I've put everything back togethere, with the new 145 Mikunis and moved the clip up one notch on the needle (so there are now two free notches below it, away from the point). Fantastically, the bike started. I had to run it on the starter for about 30 secs, but I presume that's because there was no fuel in the carbs? Anyone confirm? It runs fine now. But at around 2-4k RPM, the revs don't back off normally when I close the throttle; there's a small delay. I resume this means it's running a bit rich? Everywhere else is fine. This can;t be the jets can it, since the jets mainly affect the upper revs? Any ideas why this might be? I did readjust the mixture scres 2.5 turns from where it just seats. I've also made sure the idle ias around 1300 RPM. Any tips (Northwind?)

16-03-06, 08:12 PM	#5
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	I doubt that... 3.5's a lot, I'm running a full system, better filter, and tank spacers and I'm on 2 3/4. He's not changed the induction at all since before the rejet and it ran normally before. There's a chance you have a problem with the choke cables- did you remove them at the carb end? They can stick there, and the cables can get stuck in teh wrong position at the ends and at the y-splitter (sleeve pulls out of the mounting sometimes. __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

16-03-06, 08:58 PM	#7
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	What I mean is, I doubt it's his problem. Different systems call for differen thtings, you're right- the restrictive headers of the Micron systems fuel better low down while a more open system like mine gives more top end... But he's got a standard system. __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

16-03-06, 10:59 PM	#10
northwind Moderator Mega Poster Join Date: Jan 2004 Location: In the garage where I belong Posts: 17,083	Marginal though. Certainly not enough to have this huge impact on the idle circuit. And not when it wasn't an issue before he rejetted. This is something new that's happened as a result of the breakdown and/or rejet, and since everything else he's done is to richen things up, why would he now be dramatically lean at idle? I bet you 10p __________________ "We are the angry mob, we read the papers every day We like what we like, we hate what we hate But we're oh so easily swayed"

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16-03-06, 02:06 PM	#2
Scoobs Guest Posts: n/a	Are all cables and linkages free and lubed?

16-03-06, 02:08 PM	#3
Saracen Guest Posts: n/a	Bit naughty, ut I didn't actually lube anything. But it only happens at low revs, so that shouldn't be the cause. What's recommended for lubing the throttle cables and stuff anyway? Thanks.

16-03-06, 08:07 PM	#4
NedSVS Member Join Date: Mar 2005 Posts: 572	Yes it is normal normal to take a few seconds more cranking when the float bowls have been emptied (but perhaps not as much as 30 seconds). Your revs hovering at 2 - 4k is usually an indicator of the air pilot mixture being lean (the increase in main jet size will only have had a very small effect on the low speed running). First I'd try turning the pilot air screws out to 3 1/2 turns out and see if that helps. You may well find you need larger pilot jets with your de-baffled CCC. If you do, you can get them from Allens R&D in Nottingham (01949836733) part number N224.103 follwed by the number of the size you want (17.5 is standard, so you want 20.0 or 22.5). Hope this is of help.

16-03-06, 10:58 PM	#9
Stig Guest Posts: n/a	Following on from Northwinds point on the choke cable. Mine has been running very rich. So rich that you can smell the stink of petrol coming out of the exhaust. The choke cable was working fine. I have now stripped the the carbs off again and found that the front choke plunger had seized in the open position. This caused the front cylinder to run rich constantly, regardless of the choke position or indeed the operation of the choke cable itself. When I finally got the crappy cheese bolt undone on the front plunger and pulled it out, it was actually rusted in position. Having now sorted this problem the bike runs a lot smoother in the lower rev range. I do however need to replace the choke cable, but seeing as I never use it anyway, it can wait.