bike won't rev out

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bike won't rev out

ukpco
Hi, I'm new here as I've recently bought a mk2.

On my first proper ride the bike was great up to about 60mph then just wasn't interested when I tried to accelerate further.

In the garage it revs nicely up to about 4k - 4.5k but then just surges up and down in this range.

I've checked and cleaned the carb and fuel filters and had the carb (34mm) apart to check jets etc. I've also played with the timing, trying both the setting in the handbook (0.3" btdc) and the alternative 5 mm btdc mentioned in another post here. I have a decent spark and have tried alternative spark plugs. Nothing has helped.

Everything seems standard except I think it has a replacement coil fitted (single 12V rather than 2 x 6V in series).

Does anyone have any ideas what the problem might be or what I should try next?

Thanks
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Re: bike won't rev out

gasman
Administrator
Hi and welcome, 
Does your bike have the original ignition system or has it been replaced by a Pazon or boyer unit.
Kev

Sent from my iPhone

On 3 Jan 2015, at 17:05, ukpco [via Silk Motorcycles] <[hidden email]> wrote:

Hi, I'm new here as I've recently bought a mk2.

On my first proper ride the bike was great up to about 60mph then just wasn't interested when I tried to accelerate further.

In the garage it revs nicely up to about 4k - 4.5k but then just surges up and down in this range.

I've checked and cleaned the carb and fuel filters and had the carb (34mm) apart to check jets etc. I've also played with the timing, trying both the setting in the handbook (0.3" btdc) and the alternative 5 mm btdc mentioned in another post here. I have a decent spark and have tried alternative spark plugs. Nothing has helped.

Everything seems standard except I think it has a replacement coil fitted (single 12V rather than 2 x 6V in series).

Does anyone have any ideas what the problem might be or what I should try next?

Thanks


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Re: bike won't rev out

ukpco
In reply to this post by ukpco
Thanks for the welcome, I'm pretty sure the ignition is standard Lumenition.
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Re: bike won't rev out

gasman
Administrator
What are the frame and eng numbers,
The ignition can be as far as 7.62m btdc, have u checked the bobweights to see if they are free and moving, 
Depends on crankcase compression and no air leaks, inlet manifold, check the two rear cylinder block Allan bolts are sealed as the hole does break through into the inlet track normally silicon cures this, have you got the correct air filter fitted,
What is the colour of the plugs when revving, r the piston rings free in the grooves, and where in the country r u, my email is [hidden email]
Have you spoken to Clive at all.
Kev 

Sent from my iPhone

On 3 Jan 2015, at 17:47, ukpco [via Silk Motorcycles] <[hidden email]> wrote:

Thanks for the welcome, I'm pretty sure the ignition is standard Lumenition.


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Re: bike won't rev out

ukpco
Kev

the numbers are 78 and 80. I'm near Southampton.

The ignition is at about 7.5mm btdc now, fully advanced. I've not stripped the advance/retard down, but it seems to move as expected when advanced manually for timing.
The bike has good compression and low recorded mileage, it's certainly only done about 100 miles per year for the last 10 years, and doesn't look as though the engine has been opened up before so I'd be surprised if it's the allen bolts, although I'll check.
I'm not sure what the correct air filter is, it's got a tapered concertina type fitted. I've tried with and without the air filter and with and without choke but didn't improve things.
I haven't done a proper plug chop as I'm not keen to ride it flat out as it is at present.

Paul
 

From: gasman [via Silk Motorcycles] <[hidden email]>
To: ukpco <[hidden email]>
Sent: Saturday, 3 January 2015, 20:53
Subject: Re: bike won't rev out

What are the frame and eng numbers,
The ignition can be as far as 7.62m btdc, have u checked the bobweights to see if they are free and moving, 
Depends on crankcase compression and no air leaks, inlet manifold, check the two rear cylinder block Allan bolts are sealed as the hole does break through into the inlet track normally silicon cures this, have you got the correct air filter fitted,
What is the colour of the plugs when revving, r the piston rings free in the grooves, and where in the country r u, my email is [hidden email]
Have you spoken to Clive at all.
Kev 

Sent from my iPhone

On 3 Jan 2015, at 17:47, ukpco [via Silk Motorcycles] <[hidden email]> wrote:

Thanks for the welcome, I'm pretty sure the ignition is standard Lumenition.


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Re: bike won't rev out

gasman
Administrator
Well u seem to have covered it all, looks like you've got one of the fast ones, I tried everything on the prototype and once got 80 out of it but I was waiting for it to go bang. 
Try Clive Worrell, see how the latest boyer for the silk is going with George Silk.

Sent from my iPhone

On 4 Jan 2015, at 11:30, ukpco [via Silk Motorcycles] <[hidden email]> wrote:

Kev

the numbers are 78 and 80. I'm near Southampton.

The ignition is at about 7.5mm btdc now, fully advanced. I've not stripped the advance/retard down, but it seems to move as expected when advanced manually for timing.
The bike has good compression and low recorded mileage, it's certainly only done about 100 miles per year for the last 10 years, and doesn't look as though the engine has been opened up before so I'd be surprised if it's the allen bolts, although I'll check.
I'm not sure what the correct air filter is, it's got a tapered concertina type fitted. I've tried with and without the air filter and with and without choke but didn't improve things.
I haven't done a proper plug chop as I'm not keen to ride it flat out as it is at present.

Paul
 

From: gasman [via Silk Motorcycles] <[hidden email]>
To: ukpco <[hidden email]>
Sent: Saturday, 3 January 2015, 20:53
Subject: Re: bike won't rev out

What are the frame and eng numbers,
The ignition can be as far as 7.62m btdc, have u checked the bobweights to see if they are free and moving, 
Depends on crankcase compression and no air leaks, inlet manifold, check the two rear cylinder block Allan bolts are sealed as the hole does break through into the inlet track normally silicon cures this, have you got the correct air filter fitted,
What is the colour of the plugs when revving, r the piston rings free in the grooves, and where in the country r u, my email is [hidden email]
Have you spoken to Clive at all.
Kev 

Sent from my iPhone

On 3 Jan 2015, at 17:47, ukpco [via Silk Motorcycles] <[hidden email]> wrote:

Thanks for the welcome, I'm pretty sure the ignition is standard Lumenition.


If you reply to this email, your message will be added to the discussion below:
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To unsubscribe from Silk Motorcycles, click here.
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Re: bike won't rev out

Smokey_Paul
Administrator
In reply to this post by ukpco
Hi it may be useful to get together I live in Basingstoke and can probably help??

Cheers

Paul
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Re: bike won't rev out

Hendred
I would check out the ignition coil resistance if it has the lumenition system fitted.  Google search lumenition coil resistance and you will find the lumenition technical data sheets.  Coil resistance should be about 2.5 - 3 ohms.  If not look at changing the coils.  The two 6v coils in series work just fine on my Silk - will rev to 6000rpm cleanly.

Hope this helps

Jon
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Re: bike won't rev out

ukpco

Thanks, my coil is at 3.5 Ohms so I was wondering about changing it. Do you know what the resistance should be for each 6V coil if I go back to that? I presume 1.25 -1.5 Ohms as they're in series so the Lumenition sees 2.5 -3, but I'm no electrical engineer.

Paul
--------------------------------------------
On Mon, 12/1/15, Hendred [via Silk Motorcycles] <[hidden email]> wrote:

 Subject: Re: bike won't rev out
 To: "ukpco" <[hidden email]>
 Date: Monday, 12 January, 2015, 10:36
 
 
 
  I would check out the ignition coil resistance if it has
 the lumenition system fitted.  Google search lumenition
 coil resistance and you will find the lumenition technical
 data sheets.  Coil resistance should be about 2.5 - 3 ohms.
  If not look at changing the coils.  The two 6v coils in
 series work just fine on my Silk - will rev to 6000rpm
 cleanly.
 
 
 Hope this helps
 
 
 Jon
 
 
 
 
 
 
 
 
 
 
 
 
  If you reply to this email,
 your message will be added to the discussion below:
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Re: bike won't rev out

Hendred
Replacement 6V coils have a quoted resistance of 1.9 ohms, so two in series would give 3.8 ohms.  Not much difference from your present coil.  Do you know the make of your coil - apparently some Boyer coils require a heat sink and will overheat and fail without one?

I'll check out the resistance of my original lucas coils for comparison.  If you have some spare coils available I would give then a try.

Jon
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Re: bike won't rev out

ukpco
The coil is an Emgo (apparently a Taiwanese make). I think it's just a universal twin output motorcycle coil. Trying an alternative is my next step.

Paul
 

From: Hendred [via Silk Motorcycles] <[hidden email]>
To: ukpco <[hidden email]>
Sent: Monday, 12 January 2015, 19:17
Subject: Re: bike won't rev out

Replacement 6V coils have a quoted resistance of 1.9 ohms, so two in series would give 3.8 ohms.  Not much difference from your present coil.  Do you know the make of your coil - apparently some Boyer coils require a heat sink and will overheat and fail without one?

I'll check out the resistance of my original lucas coils for comparison.  If you have some spare coils available I would give then a try.

Jon


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Re: bike won't rev out

Hendred
Checked out my coils and the primary resistance is 1.9 ohms - same as replacement PVL coils.  

Jon
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Re: bike won't rev out

Hendred
A further thought on the subject - have you cleaned the lenses on the Lumenition head?  Might be worth a try.
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Re: bike won't rev out

ukpco
Thanks for the thought. I have given them a quick rub with a soft cloth, with no effect. I'm going to try a new coil as soon as I get the time.

Paul
 

From: Hendred [via Silk Motorcycles] <[hidden email]>
To: ukpco <[hidden email]>
Sent: Sunday, 18 January 2015, 23:15
Subject: Re: bike won't rev out

A further thought on the subject - have you cleaned the lenses on the Lumenition head?  Might be worth a try.


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Re: bike won't rev out

gasman
Administrator
Just try running the bike in a very dark place and make sure your not getting any arcing along the plug leads over the rev range you have currently.

no cracks on the inlet rubber

also check that the back of the inlet manifold is flat I've had several that where not.

try running without plug caps

wire ignition leads

no loss of water from the cooling system, I've had left hand liner leak slightly causing excess moisture in cylinder at higher revs

exhaust is clear and not choked up, take off silencer and rev the bike, does it rev better

correct ngk plugs not copies you can get from a certain site

equal compression from both cylinders

primary chain correctly set, not causing a hunting which will affect ignition timing,

check the main choke tube is it fitted in the correct plane, i.e cutout nearest engine side

as Paul might have mentioned, is the choke seating correctly

a good electrical earth

not much else to think of at the moment, let us know how you get on

Kev


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Re: bike won't rev out

ukpco
wow, lots more to try here. Thanks. I've already checked some of these, but another evening in the garage seems to beckon.

I'll report as soon as I have progress or a solution.
 

From: gasman [via Silk Motorcycles] <[hidden email]>
To: ukpco <[hidden email]>
Sent: Monday, 19 January 2015, 20:42
Subject: Re: bike won't rev out

Just try running the bike in a very dark place and make sure your not getting any arcing along the plug leads over the rev range you have currently.

no cracks on the inlet rubber

also check that the back of the inlet manifold is flat I've had several that where not.

try running without plug caps

wire ignition leads

no loss of water from the cooling system, I've had left hand liner leak slightly causing excess moisture in cylinder at higher revs

exhaust is clear and not choked up, take off silencer and rev the bike, does it rev better

correct ngk plugs not copies you can get from a certain site

equal compression from both cylinders

primary chain correctly set, not causing a hunting which will affect ignition timing,

check the main choke tube is it fitted in the correct plane, i.e cutout nearest engine side

as Paul might have mentioned, is the choke seating correctly

a good electrical earth

not much else to think of at the moment, let us know how you get on

Kev





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