bike won't rev out
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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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Hi and welcome, Does your bike have the original ignition system or has it been replaced by a Pazon or boyer unit.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
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In reply to this post by ukpco
Thanks for the welcome, I'm pretty sure the ignition is standard Lumenition.
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Administrator
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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
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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
If you reply to this email, your message will be added to the discussion below:
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Administrator
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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
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Administrator
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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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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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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: http://silk-motorcycles.6084.x6.nabble.com/bike-won-t-rev-out-tp5001188p5001198.html To unsubscribe from bike won't rev out, click here. NAML |
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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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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 If you reply to this email, your message will be added to the discussion below:
http://silk-motorcycles.6084.x6.nabble.com/bike-won-t-rev-out-tp5001188p5001201.html
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Checked out my coils and the primary resistance is 1.9 ohms - same as replacement PVL coils.
Jon |
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A further thought on the subject - have you cleaned the lenses on the Lumenition head? Might be worth a try.
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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.
If you reply to this email, your message will be added to the discussion below:
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Administrator
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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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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 If you reply to this email, your message will be added to the discussion below:
http://silk-motorcycles.6084.x6.nabble.com/bike-won-t-rev-out-tp5001188p5001218.html
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