Author Topic: C15 running issue  (Read 194 times)

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B Murphy

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C15 running issue
« on: 12 September, 2019, 11:34:04 »
Hi

From a great running bike to not so good now. The only thing I did was change all the bulbs to Led. a bit of history, the C15 was completely rebuilt with all new bearings etc. I converted it to 12v and installed a Boyer electronic ignition, new battery, coil and new OKO carb.

The bike didn't miss a beat (175 miles) until after I did the bulb change but I suppose this could just be a coincidence. the bike starts great and after about two minutes when warm the tickover deteriorates and runs very uneven. If I then leave it to cool down it runs good again and then after 2 mins runs crap and so on. Ive changed the coil for a new one and it does the same so I intend to take the carb to bits and clean it today. Any other ideas if the carb clean doesn't work, could it be a faulty electronic ignition?

AdrianS

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Re: C15 running issue
« Reply #1 on: 12 September, 2019, 12:21:14 »
Did you try changing all the bulbs back again to how it was and then run the bike?

I believe led lights are polarity sensitive - are they all wired in correctly? I would certainly put the bike back to a condition you knew it ran well with.

B Murphy

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Re: C15 running issue
« Reply #2 on: 12 September, 2019, 15:24:05 »
Put all the bulbs back and still running rough, I just cleaned the carb and still rough  :-[. I'll keep looking.

AdrianS

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Re: C15 running issue
« Reply #3 on: 12 September, 2019, 17:10:15 »
Did you put the points ignition back?

chaz

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Re: C15 running issue
« Reply #4 on: 12 September, 2019, 17:17:48 »
do you have an insulating gasket between the carb and head or is it big enough?
sounds like when warming up the fuel is evaporating, otherwise could be the coil breaking down when getting warm, I had a customer with a modern Triumph that had hoses rigged from the front to over the coils as they were getting too warm and the cooler air flow kept them coler.

A10 JWO

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Re: C15 running issue
« Reply #5 on: 12 September, 2019, 18:20:04 »
Test the battery and voltage whilst running, Boyer like plenty of volts.

B Murphy

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Re: C15 running issue
« Reply #6 on: 12 September, 2019, 21:04:32 »
"Did you put the points ignition back?"
I guess this would be the the acid test to see if the Boyer is breaking down or swap it for another EI. Do these breakdown easily? most people say install and forget.

"do you have an insulating gasket between the carb and head or is it big enough?"
There is a 1" ally flange and then rubber hose that the carb sits in so all is cool and airtight (WD spray test done) also I did ride the bike when the weather was very hot without any issue.

"otherwise could be the coil breaking down when getting warm"
I did swapped it yesterday with new coil and had the same bad running.

"Test the battery and voltage whilst running, Boyer like plenty of volts."
Did this and voltage was 12.5v when riding and then stopped after the run went to 12.9v.

Tonight I swapped the spark plug, plug cap HT lead and checked the valve clearances, the bike ran good when opened up but with an erratic tickover. So almost there. Is there a quick test that would eliminate the boyer first before revert back to putting points back in? Also could it be possible when I installed the led bulbs it inadvertently messed up the Boyer and I have to buy a new one.


berniej

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Re: C15 running issue
« Reply #7 on: 13 September, 2019, 08:25:30 »
You don't mention what you're using for your 12V rectification and regulation - is it a modern combined unit?

If the bike ran OK with the lights off before the swap to LED then I can't see what difference that would make and how it could upset your EI unit.

Cheers,
Bernie
'49 M21/B31 hybrid
'56 M21 combination
Bantam D7
C15 project
B40 Super Star
A50CC project

JulianS

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Re: C15 running issue
« Reply #8 on: 13 September, 2019, 09:33:49 »
Could be the OKO carb settings are not right. With a non standard setup it can take experimentation to get the correct settings.

B Murphy

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Re: C15 running issue
« Reply #9 on: 13 September, 2019, 11:01:37 »
Hi Berie - It's a MKIV EI and single phase power box alternator regulator.

Hi Julian - When the carb arrived I installed it straight from the box and it started after a couple of kicks. I could tell straight away that it was running great just from the tickover and blipping the throttle so took it for a ride, and 20 mile later it never missed a beat, and now after 175 miles without messing with anything apart from the bulbs.

I'm going to check all the wiring today to make sure there's nothing come loose before going back to points. Looking at all other forums with Boyer issues most of them find a cracked solder joint or loose spade end and one person said they had to change the spark plug cap to a resistor type cap. Well if it improves when I put the points back I'll stick with them.

johnan

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Re: C15 running issue
« Reply #10 on: 13 September, 2019, 14:40:35 »
Please give us feed back if you do find what is causing the problem, could be of use to some of us in the future!
My C15 has a mk4 Boyer B. EI kit waiting to be fitted, by me, but I will give it a miss until I am a bit more certain of its reliability.

Many people seem to just “fit and forget” according to what I have read, but I fitted an EI system to a Suzuki GT 250 in 1976 and it failed about 3 miles down the road on its first run...what a slog that was pushing it home!
Things must have improved since then, hopefully.

Hope you are successful in finding your fault.

B Murphy

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Re: C15 running issue
« Reply #11 on: 13 September, 2019, 20:53:35 »
I just come back from a 5 mile run still on Boyer and the bike ran very well  ??? and didn't breakdown apart from that erratic tickover. The throttle response in all ranges were good so I'm now thinking I just have a pilot issue (probably just dislodge something when I cleaned it). I've ordered another OKO carb so I'll wait till it comes and just do a straight swap and see if it instantly makes it better before I swap the EI back to points. On another note is it usual to have a small amount of smoke coming from the exhaust after a rebuild i.e. new piston and rings etc. Does this go away when the rings have bedded in?

With having the lights on tonight, when I got back home the battery was down to 12.4v from 12.9v so I'm guessing the alternator isn't putting enough back into the battery. I'll try the led bulbs again tomorrow and see what happens. Is there a better (upgrade) alternator I can just install? The one on at the moment is a three wire converted to a two wire (6v to 12v conversion).

Hope you don't mind all the questions but it's driving me bonkers.

johnan

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Re: C15 running issue
« Reply #12 on: 13 September, 2019, 23:26:20 »
Rings do take time to bed in if the cylinder was rebored, and if not rebored  it should have been deglazed to give the new rings a chance to bed in properly. A worn inlet valve guide, or missing valve stem oil seal , if C15s have them, can cause a bit of smoking too.

Perhaps the alternator rotor has lost some of its magnetism over the years and needs to be replaced?

B Murphy

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Re: C15 running issue
« Reply #13 on: 15 September, 2019, 11:33:36 »
Thanks for the replies so far.

My C15 is positive earth, so does it matter if the bracket around the coil is bolted to the frame.

AdrianS

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Re: C15 running issue
« Reply #14 on: 15 September, 2019, 13:31:46 »
No