Author Topic: Misfires above 4,500  (Read 6721 times)

Offline jon stead

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Re: Misfires above 4,500
« Reply #15 on: September 25, 2017, 04:45:39 PM »
2015 Triumph Bonneville T100 Newchurch

Offline jon stead

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Re: Misfires above 4,500
« Reply #16 on: September 26, 2017, 03:44:56 PM »
Slept on it and decided to take head off. Going to have all four spark plug holes redone, just in case.

Whilst head's away, I've been checking the wiring on the Boyer ignition and it all seems to check out. I get 2.8kohm on both of the micro coils and I've swapped them over in the hope the sooty number 3 spark plug moves to 1 or 4.

2015 Triumph Bonneville T100 Newchurch

Offline Tomb

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Re: Misfires above 4,500
« Reply #17 on: September 26, 2017, 04:42:42 PM »
I've just snapped a plug off in the head on an XS1100 Yam, head off job too so feel your pain ::)

On the upside I'll lap the valves and fit new guide seals whilst its off.
Tom
'73 CB550 with CB500 engine café racer
'62 CB77 Sprinter
'70 CD175
'78 CB550 with sidecar
'80 Z50R
And a load of old Yamaha 1100's

Offline jon stead

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Re: Misfires above 4,500
« Reply #18 on: September 26, 2017, 06:53:26 PM »
I've just snapped a plug off in the head on an XS1100 Yam, head off job too so feel your pain ::)

On the upside I'll lap the valves and fit new guide seals whilst its off.

Always a positive  :)
2015 Triumph Bonneville T100 Newchurch

Offline Rob62

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Re: Misfires above 4,500
« Reply #19 on: September 27, 2017, 07:13:37 PM »
The right decision I think jon....

Offline matthewmosse

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Re: Misfires above 4,500
« Reply #20 on: September 27, 2017, 07:39:17 PM »
Been there and done that on the snapped off spark plug with my bmw, I was dead lucky, the remains came out with the help of a flat bade screwdriver gently inserted and very gently seated with a few firm hammer blows so the blade bit into the sides of the plugs old threaded portion without spitting the ceramic bits into the cylinder, they just moved down a few mm but were held by the electrode tip. I still have a r80 bevel drive that needs a m12x1.25 timesert to repair it. The cost of the kits has  come down some way since that broke, but it has a lump of iron stopping a tap going through so it's a nasty job setting pre loads and shimmming up. Another reason to dislike bmw over Sohc Honda, too many jobs that mean building a unit up, shinning, testing pre load and then rebuilding with different shims. Honda managed to do things so much simpler yet they last better.
Got a 500/4 with rust and a sidecar and loadsa bits. nice and original and been round the clock

Offline Moorey

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Re: Misfires above 4,500
« Reply #21 on: September 27, 2017, 10:12:46 PM »
Seems like a lot of unnessesary work and cost to repair a stripped plug to me. If you try and fail you have lost nothing if you succeed you would give yourself a pat on the back. But I have spent all my working life doing this kind of work.

Offline jon stead

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Re: Misfires above 4,500
« Reply #22 on: September 28, 2017, 07:09:59 AM »
Going back to the original problem, I had a 500 that did almost the same, it was in 1972 and TBH even the Honda dealers didn't know what it was. Ran like stink when cold but as soon as it warmed up it wouldn't go above 5000 rpm, turned out to be a duff spark plug cap, fitted a new one (with those god awful metal shrouds which soon got binned) and the bike ran like a dream.  The bike was less than a year old so I didn't feel like tampering with it myself as it was under warranty, still took the Honda dealers almost 2 months to figure it out.

On Sunday night I swapped cyl 2 and 3 plug caps around and took bike out for a ride. It was dark when I got back so left bike to cool down before checking to see if fault had moved. Up bright and early on Monday morning, whipped the plugs out, no change. :-( 

It was as I put the plugs back in that I stripped number 2.

Going forward, when I get the head back on and the bike running again, I'm going to remove the Boyer Brandson ignition and reinstate the original coils and breakers. See what happens then.
2015 Triumph Bonneville T100 Newchurch

Offline kevski

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Re: Misfires above 4,500
« Reply #23 on: September 28, 2017, 07:51:54 AM »
If the problem does not move when you swap leads, you can rule out the boyer as rule, are you getting 12volts at the coils, i would be looking at valves and carburation.

Offline jon stead

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Re: Misfires above 4,500
« Reply #24 on: September 28, 2017, 08:48:35 PM »
If the problem does not move when you swap leads, you can rule out the boyer as rule, are you getting 12volts at the coils, i would be looking at valves and carburation.

Cylinder head fully overhauled, valve timing correct. Number 3 plug sooting up regardless of which of the two sets of fully refurbished carburettors I have on. If it's not the electronic ignition then I am at a loss.
2015 Triumph Bonneville T100 Newchurch

Offline Johnwebley

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Re: Misfires above 4,500
« Reply #25 on: September 28, 2017, 09:39:58 PM »
The Boyer ignition fires all 4 plugs at once,

its called wasted spark system,

  the plug No2 is its pair,,can you swap leads 2 and 3 over?


 
lifelong motorcycle rider,and fan

Offline K2-K6

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Re: Misfires above 4,500
« Reply #26 on: September 28, 2017, 09:56:56 PM »
Can you test the compression as it is? I know you won't get a hot/absolute figure for it, but it would makes a valid comparison from one cylinder to the others and see if you have any major discrepancies.

Offline Woodside

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Re: Misfires above 4,500
« Reply #27 on: September 28, 2017, 10:16:14 PM »
just a thought have you swapped the plugs around just because they are new doesnt mean they are all perfect...
possible duff one

Offline jon stead

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Re: Misfires above 4,500
« Reply #28 on: September 28, 2017, 10:32:13 PM »
Can you test the compression as it is? I know you won't get a hot/absolute figure for it, but it would makes a valid comparison from one cylinder to the others and see if you have any major discrepancies.

Bike had a rebore, new pistons and rings less than 500 mile ago. I haven't retested the compression as I'm assuming it's good.
2015 Triumph Bonneville T100 Newchurch

Offline jon stead

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Re: Misfires above 4,500
« Reply #29 on: September 28, 2017, 10:34:21 PM »
The Boyer ignition fires all 4 plugs at once,

its called wasted spark system,

  the plug No2 is its pair,,can you swap leads 2 and 3 over?


 
I probably could do that, but at the moment I'm waiting to put the head back on and try the coils that I've just swapped over.
2015 Triumph Bonneville T100 Newchurch

 

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