Hi.

Can someone explain what the symptoms are of the floats being set too HIGH are?

Also what the symptoms are of the floats being set too low?

Keihin PWK28 carb..

Floats set too high (less clearance to top of carb) are likely to leak fuel out the overflow hose. Too low (more clearance from top of carb) will not allow sufficient fuel to be carried in the float bowl and tends to run lean from fuel starvation at extended high rpm runs (not sure you will actually see this on a Trial bike)

Edited December 22, 201510 yr by wheelieman14

Thanks wheelieman,

If the floats are slightly high would this cause the bike to cut out while starting it on the choke?

It's possible, as it could be getting too much fuel.

 

The choke isn't a choke (a flap to restrict air).

It's an enrichment circuit, basically a big jet of around 0.6 or 0.7mm that allows fuel to bypass the pilot and main jets to aid starting.

It won't cut off the main and pilot jets, but aids them by increasing the fuel to air (which is set or more correctly not restrictable any further)

 

So if you have fuel overflowing out of the float bowl (because the floats are high) it'll find it's way into the engine (not just out of one of the carbs breather tubes), plus with the "choke" on, it's possible it could flood up, but whipping the plug out after it's stalled and checking how wet it is would confirm this or not, also you'd need to consider the fact if it was flooding bad, would it start in the first place?

 

If the floats are low, as already described, they tend to run lean (and hot).

 

How much it does either of the above depends on how lean or rich it actually is, but usually if it's very lean, it won't settle to an even idle and when rev'd they tend to "ring a ding ding" more on the over run.

Too rich and it bogs down and splutters or stalls, if it starts and runs at all.

 

 

You could also get the same sort of results from an ignition issue, if it can't ignite the fuel at the correct time!

 

What is your actual problem?

Edited December 23, 201510 yr by goudrons

Hi goudrons thanks for that reply that was really helpful for me,

The bike doesn't seem to settle to a nice even idle and has that tinny overrun..

Iv only owned the bike a few weeks it was good when I got it but after cleaning the carb for the 1st time I tampered with float heights and had them set too high ( fuel was coming from the overflow when fuel turned on )

So after a few tweaks lowered them.

I just don't think I've got them set right YET.

1st thing in the morning when I start the bike , I turn on fuel put the choke on and kick it over, it'll start 1st kick then after 2-3 seconds it'll start to bog out and stall if I'm not quick in flicking the choke OFF...

Iv followed the pdf from Lampkins on float adjustment, cleaned the needle valve-seat , cleaned the carb/ jets , holes countless times now.

But as you've described it's just not idling spot on

They don't usually run well on the "choke" after starting, like I said, it's an enrichment circuit rather than a choke, it's just an aid to drawning fuel into the cylinder to fire it up.

 

I fire mine up on choke from cold and within a few seconds flick the choke off and then warm it up, until it's properly warmed up, mine won't idle that well either.

But once warm, it idles and runs right.

 

A ringy dingy, (when warmed up) engine on the over run that has an uneven, hunting up and down idle, sounds like it's lean. Applying a little choke makes it better as you are richening it up

A dull, flat sounding engine tend to be running rich. Applying a little choke makes it worse as it's now too rich.

 

If it's lean, it may not be solely due to carb, problems with ignition can give the same results, as can air leaks (head, base or reed cage gaskets or crank seals).

 

Just on the off chance, check the coil.

There's a push fit, spade connector to the bottom of the coil, the connection gets grubby and the spade connector rattles loose, this can give make the bike run all wonky.

Give the connector a clean and a small squeeze to tighten it up.

Edited December 23, 201510 yr by goudrons

I should also have added that Beta's don't tend to like normal 95 octane unleaded as it makes them ping and knock a little.

 

They like 98 or 99 octane Super unleaded.

thanks again , this is a picture of my plug iv just took out ... wet!

 

 

 

 

What gap is that plug set at ? It may be the angle of view but it looks too small.

0.6

Put a new plug in, they don't like being wet.

B4ort ...

That's not solving the issue, there is a reason the plug is getting like that.

Cheers though

Are you sure about that gap ? That looks more like 0.15mm or 0.006 inch ! ( commonly known as six thou)

Just humour me and check it again ?

Kind regards

0.6mm (0.024") spark plug gap should be fine (though your gap seems too small in that pic), but that spark plug looks like it is running very rich - either too much fuel, or not enough air. Are you running a clean air filter without too much oil on the element?

 

Check your Main Jet & Pilot Jet and Needle clip position. Maybe you are just running too rich?

 

Also, since these engines run at relatively low RPMs, you can get proper lubrication running your Pre-Mix Fuel with 98 Octane gas and Oil mixed at 80:1 (helps prevent spark plug fouling and gives better burn inside combustion chamber). This also assumes that your Ignition Timing is set properly.

 

My bike also only needs the Choke, when engine is cold and I can shut Choke off within a few seconds of starting it up.

Edited December 23, 201510 yr by wheelieman14

B4ort ...

That's not solving the issue, there is a reason the plug is getting like that.

Cheers though

A fouled plug can, and will, cause erratic running. You might have solved the original issue, but won't know with a duff plug. What's to loose ?

Edited December 23, 201510 yr by b40rt