Engine set up update.... with another question!

[AndyB57]

I've not had much time to work on the 3 1/2 over the last month or so but have now fitted new HT leads and caps, switched and initially setup the carbs. A quick couple of rides seem to show it starts as easily as ever (2nd kick), the tickover and faster running are improved, and so far the front plug doesn't seem to be getting as sooty - could be better though. What I now have though is some initial hesitation and popping when opening the throttle, but I'm going to try altering the needle height and some more fine tuning.

However...... I'm getting a lot of very buzzy vibration from around 2000rpm up. I can feel it through the seat and bars, and when revved on the centre stand the bike moves. Any thoughts about what may be causing this?

[BumbleBee]

Just a thought, to compare it to someone else's similar model. Back in the '70s "smoothness" had a somewhat wider definition than the bikes made these days.

[MickeyMoto]

Have the carbs been balanced since the initial setup?

Ignition timing?

Engine bolts tight?

[AndyB57]

Just a thought, to compare it to someone else's similar model. Back in the '70s "smoothness" had a somewhat wider definition than the bikes made these days.

Les M had planned to ride over and take a look/listen and let me hear a sorted engine, but weather,family visits, etc got in the way. I agree it would be useful to hear another 3 1/2 though.

[AndyB57]

Have the carbs been balanced since the initial setup?

Ignition timing?

Engine bolts tight?

I have balanced the carbs but will do so again - they could well have dropped out of sync with all my fettling! Timing was set up when the belt was changed just before I bought the bike, and given starting is never a problem (fingers crossed) I thought it should be ok, but I should track down a strobe and check it again. I checked bolts, all seemed to be good and snug.

[MickeyMoto]

Alarm bells ringing. The ignition timing is set on the left end of the camshaft. The generator rotor has the timing marks. If... the ignition is standard...

[AndyB57]

Alarm bells ringing. The ignition timing is set on the left end of the camshaft. The generator rotor has the timing marks. If... the ignition is standard...

You mean it sounds more like the timing being out?? From what I've seen on the various videos it all seems to be the original system with black transducers and red ignition. I'll get hold of a strobe and check the timing.

[MickeyMoto]

Hi Andy,

No, not saying that as vibration could be a lot of things, including normal characteristics of the engine. My fear is that mention was made to timing being set when the belt was changed. Moving the alternator is of no benefit, as far as I know.

As the belt was changed, it may be worth checking the valve timing...

Mike.

[AndyB57]

Hi Andy,

No, not saying that as vibration could be a lot of things, including normal characteristics of the engine. My fear is that mention was made to timing being set when the belt was changed. Moving the alternator is of no benefit, as far as I know.

As the belt was changed, it may be worth checking the valve timing...

Mike.

Thanks for the clarification Mike.

Over the next few days I'm going to re balance the carbs, check the valve clearances again and use the latest addition (of many over the last few months....) to my toolbox to check the timing. If things haven't improved after that I may stick to bicycles!