IP2 Misfire

[gripper]

I'm still plagued with a misfire on my IP2. I've substituted the coils, plug leads/caps, removed the retard box, sidestand cutout switch and I'm now beginning to suspect the carburation. I've replaced the o rings in the SU choke system, cleaned the float chamber and the piston and vacuum chamber. The main jets have been set with a digital vernier caliper. The symptoms are: Bike starts and once initially warm it will run on both rotors at tickover. As the revs are increased between 1500 and 2000 there is a misfire on one rotor that clears as revs are increased towards 2500. After the bike has done about 3 miles the problem dissappears and runs normally. Up until then it's like riding a pogo stick and not much fun. I've fitted a tap in the LHS of the tank to ensure a good supply of fuel to the LH carb but it has made no difference. Any ideas gratefully recieved. Straws clutched at.Dave EOn another subject, the speedo (french) only reads up to 70mph.

[gripper]

Fixed the speedo, opened the throttle further

[Dell Boy]

Sounds like spark plugs to me. The one I had in the eighties ate them. I`ve got an ice cream tub full of used ones.Derek.

[Interpol2471]

I found my IP2 ran better on C9E plugs when cold but CR9EIX when hot. Who knows the wonders of spark plugs

[gripper]

Might have a result here. After my engine rebuild, and despite the battery being not that old, (18 months) it didn't seem to spin over as fast as I'd expect. The bike hasn't been out recently due to the shite weather and has been hooked up to an Accumen charger for a couple of weeks. Went to start it up to ward off my withdrawal symptoms and it didn't really want to know. Connected it up to a car battery and it started well and didn't seem to be misfiring ( that was before the smoke detector went off in the garage) So, Battery may be strong enough to just start it but the voltage drop during this process gives poor supply to the ignition. After about 2 or three miles, battery is charged back up to ramming speed, problem goes away. Does that make any sense to anybody out there? remedy, get hand in pocket for another new battery. I thought Varta batteries were the bizz, maybe not.

[Dell Boy]

I have found Varta batteries the best out of many but thats not to say you cant get aduff one.I rode around central London in the late 80`s doing building site inspections on my IP2. It was constant stop start with the day riding lamps on & stop light almost permanently on & this killed the Yuasa batteries & other makes I used then.I then copied the R.A.C. IP2`s & installed a bloody great car battery in the top box which helped a lot. I did a lot of 1,2,3 steps & bump as well in London traffic. Always a hairy procedure especially if the clutch was dragging as usual & wouldn`t disengage. I must have been fit then!!!With any electronic ignition system a poor battery will affect its performance.Best thing to do is buy a Commander. Twin batteries plus all the other improvements over the air cooled model.Out on the Red Commander today & in these freezing conditions it was retarding beautifully & ticking over at 400 revs. I shall have to do some investigation work on the Grey one to get it to retard at around 88 to 90 degrees. It has been getting steadily worse & only retards above 105 degrees now.Derek.

[johnbirchjar]

Perhaps the Accuma charger cant keep up with the hammering that batteries take when the tempreture drops below zero,added to the fact that (so Iv'e been led to believe) the current is still "live" even with the ignition off,thus causing a drain on the battery. I expect to have the same problem with the Classic when I next fire the old girl up(even if I have disconected the battery)when the weather improves, so I will just do a "jump start" of the car . Take care,J.B.

[gripper]

I've just sold my Commander! I must say that two cheap and nasty batteries never failed to spin the Commander over nicely.

[gripper]

I found a couple of bad connections at the fuse box where I'd been removing and reconnecting the retard box and that seems to have sorted the misfire. I've had the bike hooked up to an Accumen for a week and the battery was up to about 12.8v but wouldn't crank the engine. Connected a car battery via jump leads that was showing about the same voltage and away it went. Disconnect jump leads after the bike is warmed up, won't start. Charged it again with a car type charger off the bike. still won't start without the car battery. Looks like sitting around waiting for an engine rebuild isn't the best for Varta batteries despite the occasional trickle charge. I'll get the local battery shop to test it under load. (think I know the result) Then decision time, gel or lead acid. (The last thread on batteries was some time ago, anything changed?)

[gripper]

Just fitted a new battery and one of Graham's digital ignitions (12v coils from My old Commando, no ballast resistor) starts and runs on both rotors from cold instead of coughing and farting and cutting out. pick up is good and the tickover is rock solid. Result only cost £210 and lots of garage time. Opened up the Sparkright unit and it looks like someone has been poking around in there. Odd mounting, tie-rapped to the regulator with two bits of tin and a couple of pins to stop it all slipping out the bottom of the electrical bay. Not proper engineering compared with the rest of the bike.

[gripper]

The misfire until properly warmed up returned and was becoming a pain in the ar-e and I could live with it no longer. Even after the retard of the digital ignition kicked in, the bike was still not picking up cleanly. Everything was good once the engine was hot. I removed the carbs and cleaned them even though there seemed to be little gum or dirt to deal with. On Richard's advice I replaced the float needles with viton tipped ones from Burlen. (very reasonable at about £20 including p&p and came with new needle seats) I reset the float height and made up an adaptor to set the main jet using a dial test indicator. This has worked very well with good running from start up. I don't think the float needles or the float height or the main jet height were the problem. I think something was stopping the carb slide from lifting cleanly until the carb body was hot and slightly expanded. So for the time being, I love it again.