Author Topic: Odd idle issue with PHBH30's  (Read 2431 times)

Offline v65tt

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Odd idle issue with PHBH30's
« on: January 21, 2016, 02:00:10 PM »
My V65TT ( and now V7TT) has always had an odd idle problem, its never caused me any problems but since the V7 Engine has gone in I have decided to dig deeper.

So when its sat idling happily around 1200 rpm I close both fuel taps and the idle goes up to about 1500 slowly, open the taps and it drops back down.  ( prob was same with the v65 engine..!)


any ideas?
« Last Edit: January 21, 2016, 02:01:07 PM by v65tt »
Iain

1984 V7 TT ( 2015 v7 stone powered TT )
1986 V65TT
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Offline Tom

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Re: Odd idle issue with PHBH30's
« Reply #1 on: January 21, 2016, 02:50:16 PM »
Mixture leaning out with less fuel. :tongue: a guess.
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Offline v65tt

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Re: Odd idle issue with PHBH30's
« Reply #2 on: January 21, 2016, 02:52:48 PM »
id figured that bit for myself   ;-)


so smaller main jet , or smaller pilot or alter float height?

« Last Edit: January 21, 2016, 02:55:11 PM by v65tt »
Iain

1984 V7 TT ( 2015 v7 stone powered TT )
1986 V65TT
2016 SWM SILVER VASE 440
1974 HONDA XL250 MOTOSPORT

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Offline Tom

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Re: Odd idle issue with PHBH30's
« Reply #3 on: January 21, 2016, 02:57:24 PM »
Yeah, something like that.  A little experimenting on your part.
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Re: Odd idle issue with PHBH30's
« Reply #3 on: January 21, 2016, 02:57:24 PM »

Offline Two Checks

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Re: Odd idle issue with PHBH30's
« Reply #4 on: January 21, 2016, 03:09:45 PM »
If your plugs are a nice tan, don't change a thing.
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Offline Triple Jim

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Re: Odd idle issue with PHBH30's
« Reply #5 on: January 21, 2016, 03:23:55 PM »
The main jet won't affect idle.  As you know, speeding up as the fuel level in the float bowl drops indicates you're a little on the rich side.  I don't know that carburetor offhand, but adjusting the idle mixture for maximum RPM should do what you want.  If you have air screws, you would open them a little to find the maximum.  If they're fuel screws, you'd close them a little.  If unsure, you'll know as soon as you turn one, since going any richer is sure to slow the engine even more.  If the mixture screws are at maximum lean already, then you'd need to go one or two pilot sizes smaller, but as stated, if you're not blowing black smoke at idle, it may not be worth the trouble.  I bet you can adjust it leaner with the screws though.

I like to set mine slightly rich.  That is, RPM on the edge of dropping if I go any richer, rather than right in the center of the max RPM range.  I find that warmups are easier that way, with less fiddling to keep it running when cold.
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Offline Curtis Harper

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Re: Odd idle issue with PHBH30's
« Reply #6 on: January 21, 2016, 04:45:49 PM »
I really have to ask, Why are you concerned with what the idle is when you shut the gas off in the first place?
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Offline jacksonracingcomau

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Re: Odd idle issue with PHBH30's
« Reply #7 on: January 21, 2016, 05:45:22 PM »
 
I really have to ask, Why are you concerned with what the idle is when you shut the gas off in the first place?

 :1:


Online Chuck in Indiana

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Re: Odd idle issue with PHBH30's
« Reply #8 on: January 21, 2016, 06:52:42 PM »
I think he's trying to figure out whether the idle jet is the right size. I go for a *little* big. Helps cold start driveability.
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Offline guzzisteve

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Re: Odd idle issue with PHBH30's
« Reply #9 on: January 21, 2016, 07:13:20 PM »
If the mixture screw is 1turn out or under= go smaller
If mixture screw is 3turns out or more= go bigger

This is for the short tip mix screw

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Offline v65tt

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Re: Odd idle issue with PHBH30's
« Reply #10 on: January 22, 2016, 03:46:49 AM »
I really have to ask, Why are you concerned with what the idle is when you shut the gas off in the first place?

I only have an 8 litre fuel capacity and as its running too rich I'm hoping to get a fuel economy improvement by sorting out the fueling
Iain

1984 V7 TT ( 2015 v7 stone powered TT )
1986 V65TT
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1974 HONDA XL250 MOTOSPORT

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Offline Curtis Harper

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Re: Odd idle issue with PHBH30's
« Reply #11 on: January 22, 2016, 07:17:54 AM »
and then I am assuming that you put carbs on the 2014 motor?
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Offline v65tt

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Re: Odd idle issue with PHBH30's
« Reply #12 on: January 22, 2016, 07:21:36 AM »
Yes on the 2014 now. Prob was same when on original 650 lump.

Starts well and rides fantastic
Iain

1984 V7 TT ( 2015 v7 stone powered TT )
1986 V65TT
2016 SWM SILVER VASE 440
1974 HONDA XL250 MOTOSPORT

http://www.streffords.net

Offline Curtis Harper

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Re: Odd idle issue with PHBH30's
« Reply #13 on: January 22, 2016, 07:28:28 AM »
And what is the fuel mileage now?
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Offline v65tt

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Re: Odd idle issue with PHBH30's
« Reply #14 on: January 22, 2016, 10:45:24 AM »
hard to be accurate but around 40 miles on 4.5 litres or 80 miles on a tank


Right had afternoon in workshop to compare needles and jets between the 2 V65TT's i have.


My spare white TT has 112 main jet  and a 38 pilot  ( has K&N filers)

My V7TT has 115 main jet and a 40 Pilot.  Put new plugs in this afternoon and they came out 10mins later sooty black.


Compared the 112 to the 115 and the diameter of the hole is huge on the 115.

Got a set of small drill bits and a 1.2mm drill bit falls through the 115's....I think at some point in the past someone has drilled out the mains.

Swapped the 112 and 38 pilots from the white bike's carbs into the V7TT and after 30 miles the plugs are just on the rich side of perfect ( ideal for me) and and the idle is no longer rising as the fuel runs low with the taps off

Will monitor for a few weeks and see how we do!
« Last Edit: January 22, 2016, 11:20:52 PM by v65tt »
Iain

1984 V7 TT ( 2015 v7 stone powered TT )
1986 V65TT
2016 SWM SILVER VASE 440
1974 HONDA XL250 MOTOSPORT

http://www.streffords.net

 

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