Bike difficult to start

[rowpy]

Hi All,

I've just bought a Strada 500 as a project – it’s not in the best of shape and will need some work. I bought it from NLM who had it running before they sold it although didn't give any more guarantees than that. At first I couldn't get it running but have since fixed the valve clearances and have had it running a few times since.

However it is very difficult to get started – at the weekend I must've kicked it over a couple hundred times and got it started about 5 or 6 times. It was improved when I cleaned the jets out and also it was missing the tube which connects the two carbs together which I have replaced.

When it did start it sounded great except it was backfiring from the rear cylinder and wouldn't run at all with the chokes off. Also it died if I gave it too much throttle, or not enough. If it didn't start within the first four or five kicks then it wouldn't start at all and I had to leave it for a while before trying again – presumably the engine is flooding?

The previous owner tried to café racer it so it has pod air filters on and Lafranconi silencers. I'm not sure whether the previous owner has changed the jets on the carbs.

So my thoughts are that it’s running lean, the carbs aren't balanced or that possibly the timing is out? Also perhaps something is wrong with the float level maybe if it’s flooding that easily? Anything else worth checking?

Any help would be very much appreciated - also if anyone's in South East London and wouldn't mind popping over to take a look then I can repay with beer and/or tea!

Cheers,

Rowan

EDIT: Yesterday evening I had another go at starting it and it started first kick with both chokes on and ran for about 5mins before it cut out - it seemed to do this no matter how much throttle I gave it. I tried to restart it and it started first kick again but died about 5 seconds later. Seems that once it's warm it doesn't like to run. I tried it without choke on but it wouldn't start at all then. It then wouldn't start again - possibly the engine flooded.

[hendre]

...It was improved when I cleaned the jets out and also it was missing the tube which connects the two carbs together which I have replaced.

When it did start it sounded great except it was backfiring from the rear cylinder and wouldn't run at all with the chokes off.

the tube between the carbs is de balancing tube, if it is open it suck extra air into the mixture... running much too lean

...Also it died if I gave it too much throttle, or not enough. If it didn't start within the first four or five kicks then it wouldn't start at all and I had to leave it for a while before trying again – presumably the engine is flooding?

pfew, could be a lot of things. seeing where you cam from a good carb cleaning, replacing all carb seals and o-rings and a proper sync could help out a lot. How is the ignition, do you get spark when the engine is warm?

...The previous owner tried to café racer it so it has pod air filters on and Lafranconi silencers. I'm not sure whether the previous owner has changed the jets on the carbs.

loose the pod filters and get a stock air filter, hard to get but they run so much better on that
Keep the Lafranco's, they should not be any problem

... EDIT: Yesterday evening I had another go at starting it and it started first kick with both chokes on and ran for about 5mins before it cut out - it seemed to do this no matter how much throttle I gave it. I tried to restart it and it started first kick again but died about 5 seconds later. Seems that once it's warm it doesn't like to run. I tried it without choke on but it wouldn't start at all then. It then wouldn't start again - possibly the engine flooded.

could be that the tank vent is clogged up (so you end up with a vacuum tank after a while), could you try and start/run with the tank cap opened to see if this solves this issue? Have you cleaned the taps? could be that gas is seeping through and filling the carbs slowly but the flow is not enough to cope with the running engine...

[72degrees]

It's ignition - it's always ignition Seriously, you can't rule out the ignition stator winding insulation breaking down when hot. Test the resistance immediately after it has stopped running if you can get it going again. Even better, hook the multimeter and watch the resistance on starting and as it fails. Float needles OK?

If one cylinder is working better than the other a swap of components might be revealing. You could switch the carbs over fairly easily. You can also switch the wiring to the transducers to check if one of those is the culprit. It could also theoretically be the pickup, though I've only had them fail so as to give no spark on either cylinder.

[rowpy]

...Also it died if I gave it too much throttle, or not enough. If it didn't start within the first four or five kicks then it wouldn't start at all and I had to leave it for a while before trying again – presumably the engine is flooding?

pfew, could be a lot of things. seeing where you cam from a good carb cleaning, replacing all carb seals and o-rings and a proper sync could help out a lot. How is the ignition, do you get spark when the engine is warm?

I've cleaned the carbs but haven't replaced the seals etc - I'll order some new seals and give that a go. I also haven't been able to balance the carbs - primarily because I don't have a vacuum guage but I also don't think I'd be able to run the engine long enough/get the engine warm enough to do it - but it's definitely on my to-do list. I haven't checked the spark while it's warm - next time I get it running I'll do it.

... EDIT: Yesterday evening I had another go at starting it and it started first kick with both chokes on and ran for about 5mins before it cut out - it seemed to do this no matter how much throttle I gave it. I tried to restart it and it started first kick again but died about 5 seconds later. Seems that once it's warm it doesn't like to run. I tried it without choke on but it wouldn't start at all then. It then wouldn't start again - possibly the engine flooded.

could be that the tank vent is clogged up (so you end up with a vacuum tank after a while), could you try and start/run with the tank cap opened to see if this solves this issue? Have you cleaned the taps? could be that gas is seeping through and filling the carbs slowly but the flow is not enough to cope with the running engine...

I hadn't thought of that - I'll give it a go with the tank cap open. I've cleaned the taps and have cleaned out the tank as best I can a couple times - there was some crap in there.

It's ignition - it's always ignition Seriously, you can't rule out the ignition stator winding insulation breaking down when hot. Test the resistance immediately after it has stopped running if you can get it going again. Even better, hook the multimeter and watch the resistance on starting and as it fails. Float needles OK?

If one cylinder is working better than the other a swap of components might be revealing. You could switch the carbs over fairly easily. You can also switch the wiring to the transducers to check if one of those is the culprit. It could also theoretically be the pickup, though I've only had them fail so as to give no spark on either cylinder.

I have checked the resistance once and remember it being ok but can't recall what it was now - I'll give it another go and see if I can test it while it's running too. The float needles looked ok to my novice eye - I also tested them by running fuel through with the float bowl off and pushing the float up to see the flow stop - I forgot to check the level though which I'll do next. I'll have a go at swapping over components although at the moment it's so difficult to start that it's hard to do a comparison.

It's going into the garage for a few days to have the pistons in the brake calipers un-seized and seals replaced so I'll ask them to take a quick look at the carbs and ignition to see if there are any obvious problems that I'm missing.

Thanks for the help guys - I'll let you know how it goes when I get it back from the garage!

[Jaydub]

An easy one to check that may cause similar problems especially as the air filter is missing - are the inlet rubbers leaking? They are not the best design and really need the air filter to support the weight of the carb's.
Also, we have a running issue with our 500 that shuts off the electro magnetic fuel tap after a period of running - anywhere between a couple of minutes and a twenty mile ride.
Due to being simple slide carb's they can be got pretty close balance wise without even running the engine. I know final setting up will need to be done with the bike running but just adjusting the cables so that both slides operate at the same time will be plenty close enough most of the time. Similarly, incorrect jets may manifest themselves as a problem whilst riding but are unlikely to affect the running under the conditions that you describe. Best of luck, I've just stripped, rebuilt and synch'ed the carb's on ours and it was well worth the effort apparently...

[rowpy]

I did have a look before and they looked ok - would it be a visible leak? Is there a way to check aside from visual inspection?

I don't have the electro-magnetic fuel taps luckily so that's one less thing to go wrong.

I'll have another look at the slides to see if they're visibly off - I might replace the throttle cables before I do though. My to-do list getting longer and longer - all good stuff though! Thanks guys!

[boris tarpit]

. . . I check for leaks on the inlet by either spraying WD40 or 3 in 1 oil on the suspect component and listening for a change in engine note or funny smelling smoke from the exhaust as the oil is sucked thru . . . Synchronise the carbs by resting a piece of thin stiff wire under the slides to magnify the movement, it isn't as exact as vacuum guages but will set it up well enough to run . . .

[72degrees]

Silly me, I really meant check the output voltage from the stator when *running*. I've only ever tested the resistance when not running. Still worth comparing hot with cold.

My old SWM used to eat ignition windings. I went all the way to Doune in Scotland for a hill climb to find it would only run for a minute or so before dying. I even attempted one practice run by pushing it to the line and doing a sort of one man Lemans start. That was diagnosed by someone with a voltmeter. Cold, started and running - some volts. After a minute or so running the voltage rapidly dropped to zero.

My GFR ignition winding also failed slowly such that a new plug (after having to be recovered) lured me out on a short ride. Fortunately I only was on few miles circular tour and had another clean plug with me which just about got me home after it stuttered and stopped again. Sure enough - below par ignition winding resistance (rewound by West Country Windings who also did the Bosch item on thje SWM for me)

A Morini should run on just one cylinder.I did several slow miles two-up in France, years ago, on one pot to get to a hotel where I eventually used the spare transducer and pickup I had packed to get back on the road (with mismatched components but two functioning cylinders).

Running with the tank open is certainly a good test. I had that problem with a motor mower with a Briggs & Stratton engine. No obvious vent in the tank cap to clean, but a new cap cured it.