Commander running problems

[pete]

Hi All, I'm looking for a few suggestions. My Commander has been running fine since I got it a few years ago. I've had a few niggles here and there but it never failed to start or run properly. I'm a fair weather rider and it was laid up over the winter. I took it out for a run a couple of months back during a nice day but it was dark and cold by the time I came home. I noticed that it was over- ing and decided to pull and check the thermostat. ...... No thermostat. A helpful previous owner had removed it. I got one from Graham and rebuild the water pump while I was at it. While I was at it, I also fitted Graham's anti-smoking kit in the form of a replacement right hand inlet pipe with a small side branch on it to connect the intermediate plate oil tap tube up to. I also put in a pair of Iridium plugs. After the work I took it out and it ran fine initially and then lost power. It felt like it was running on one cylinder and bellowed clouds of smoke out the back. I came off the motorway, stopped and the smoke was largely coming from the left side exhaust. I drove back through traffic and it smoked badly for a while and then ran ok again. All the relevant electrical connections seemed fine, I put back in the ordinary spark plugs and took it out again. It was a bit lumpy at first and then seemed ok but not great. Up onto the motorway and it just died without warning. Started again but only ran with very low power, banging and popping all over the place and wouldn't rev. I had the shame of coming home in the back of a recovery van. I thought it might be ignition related as it sounded like it was heavily retarded when it was running. The man in the van thought it was fuel. I checked the fuel vacuum line and it's ok and there's clean fuel running through the in-line filter. I also checked the charging voltage and it's exactly as it should be at all revs. From cold, the motor now starts, runs and revs but it's lumpy and hunts a bit. I haven't had it out again yet but loading the motor with the back brake stalls it almost immediately so still no power. Any suggestions ? Pete

[Interpol2471]

I guess first thing would be to check what you changed or disturbed if the bike was ok before the work, I see you say it ran but ran ok?I would check the inlet pipe you changed for air leaks first and any other pipework removed, worse case put it back as you had it and start from there. I am sure Malc or Richard may well have some technical advice soon, good luck

[graham]

What colour is the smoke? Is it white/ pale grey. In which case it's a carburettor either flooding or leaking past the choke O ring.It's not unusual for the choke O ring to suffer during cleaning if you don't remove the choke mechanism first. If the O ring fails, it allows neat fuel to flow freely into the inlet tract. It doesn't just richen the mixture, it pours in! Within seconds, fuel drips out of the exhaust port and the engine refuses to run on that side. Graham

[pete]

Thanks for the response guys.I contemplated reversing all the changes I made but I'm not convinced that they are directly the problem and I don't really want to undo everything if I can avoid it. The smoke was white/pale grey rather than thick oily black smoke. I'm not sure how I'd check the choke O-rings in the carb without pulling it and I'd rather not do that if I can avoid it. Besides, it's not smoking any longer. It smoked a couple of times when I was out on it and the smoke was on the left side whereas I had removed the right carb but not the left. Pete

[wust588]

How is it running now?From the way you describe the problem, it sounds almost as though you might have a blocked fuel filter, and / or failing ignition box.Sudden clouds of smoke can indicate a sudden unblocking of the frame drain into the left carb.For it to happen after you made your mod maybe coincidence because it suggests several causes at the same time!Just a few thoughts.

[pete]

Ok, I had a bit of time over the weekend to have a poke at it and while I haven't had it out on the road again, it's still not running right. It starts, runs and revs but dies for no apparent reason. It runs unevenly (lumpy idle) with a small fluctuation in the revs and sometimes refuses to rev and just dies when you open the throttle or if it does rev it's sort of splutters and won't rev evenly. It's not smoking heavily any more. On the ignition side I checked the flywheel sensor and both resistance and gap were right. I pulled each plug lead in turn and connected up a spare plug to the disconnected lead. Spark seemed to be strong and continuous on both sides and of course it ran (badly) on only one rotor on either side. Once it warms up, the temp sensor switches and the ignition goes into idle mode, the revs drop to about 600 rpm and you can hear that rattly 2 stroke sort of exhaust note that I associate with a heavily retarded ignition. When you rev the engine, it sounds like the ignition is remaining heavily retarded. On the fuel side, I replaced the vacuum hose from the intake manifold to the fuel tap as the end rubbers had become brittle and could well have been leaking. I also topped up the damper oil level in the carbs which was embarrassingly low . I'm going to check the fuel tap flow rate and make sure the fuel filter isn't blocked. Pete

[graham]

If it still has the original carbon leads, try replacing them.Graham

[johnbirchjar]

How about the vac: pipe for the advance and retire? the one behind the vac:pipe for the fuel.J.B.

[pete]

The main problem has been solved and of course it turned out to be trivial to fix if not to find..... Someone here suggested that I check the fuel filter. It looked fine to me and I could see fuel in it so I thought it was ok. I suspected the fuel tap might not have sufficient flow so I pulled the fuel connection on the left hand carb, pulled a vacuum on the tap and nothing. I pulled the hose into the fuel filter and got lots of fuel. Blocked fuel filter. This is worth noting. I had noticed a while ago slight weeping of fuel from the connections on the fuel filter so I replaced the spring clips with jubilee type clips putting more compression on the hoses. A combination of heat and fuel has obviously softened the plastic of the fuel filter and the extra force of the jubilee clips caused both the inlet and outlet pipes on the fuel filter to compress to the point where the outlet one was almost completely closed. Check your fuel filters I had the bike out for a test run last night and there were no problems on the motorway. Low speed was another matter. There was obviously more than one thing going on here. She will start ok and runs on fast idle ok but when the choke is off she's idles very rough and at very low revs of about 400 to 500, if the rev counter is to be believed, which sounds about right. She's slightly less rough when fully warmed up but still not great. I tried to balance the two sides using a balance gauge and the idle speed adjusters on the carb outlet manifolds. I could adjust the balance with the screws but I could not increase the idle speed. The screws seem to have no effect at all apart from a very minor change to the balance. Also, when riding it at low speed it seems as if it's trying to pull the ignition into retard mode if I let the revs fall and it is often reluctant to rev out of retard mode again, making low speed stop/start riding in traffic extremely difficult. We're slowly winning but I could still do with a few more suggestions from the mine of experience out there. Pete

[pete]

I also tried changing the plug leads as Graham suggested and it made absolutely no difference at all. A thought struck me. The temperature sensor on the front of the engine (for the ignition module) is referred to as a thermistor. It has 2 wires going to it and in my case it is a temperature sensitive switch. It's open circuit at low temp and at about 65 deg it switches to closed circuit. Is this correct ? The parts catalogue refers to it as a thermistor which in my world is a temperature sensitive resistor, like the sender for the temp gauge. Pete

[Interpol2471]

That is the correct operation it just switches in the retard circuit after the engine warms up.