Griffon Gremlins

[Dick F]

Can anyone at all point Rob Thornton and me in the right direction in the problem griffon that Rob has, as we are now ready for Hospital treatment!

The 250 bike has had a new piston fitted ,after the old one gave up last year and bored out to suit, prior to that it used to bog down at corners, and low revs also, changing jets ,float levels checked, air leaks etc it will not run when load is put on it, pulling away will just gas up and stop?

We have tried three 900 concentric carbs , and will start but you have to turn the fuel off immediately,and then it will clear and rev clean but when fuel is turned on again it bogs down and stops.
We took a villiers S25 off robs Hawkstone and it ran straight away , although down on power.

Any answers on this on going saga appreciated. regards Dangerous Dick

[dave higgins]

Hi dick, a little trick i have learnt is that not all amal mk1 concentrics have their pilot drillings bored out any more then the standard .25 setting, in effect, no matter what size pilot jet over 25 you fit, you will not benifit.
Its the first 1/4 of uptake ( ie pilot jet), that gives the pull away & if by thinking that you have tried the bigger p/jets & not worked, then have gone on to overcompensate in the mid range, then this could give you your over rich bogging down.
As for the last paragraph, then the float bowl is to high, or float needle not seating. hope this helps. dave

[Dick F]

griffon gremlins

Thanks Dave,
What you have said regarding the fixed jet drilling is correct, as a matter of fact Rob will in due course do an article on the Forum or the Leading Link in respect of the problems he has had with a new 600 series on his Anglian!

I expect he will read this and be able to explain the problems we are having better than I can ! .

Thank you for your input and we will see where we go next Dicky

[Colin Sparrow]

We have tried three 900 concentric carbs

With three Concentrics I expect it's running a bit rich. Try two.

[Brian Catt]

Can we have an expert to tell 24ME owners how to set up their twin carbs at altitude????

[riflegreen]

Dick ,

Is it a 930 or a 932 Concentric . I have a 900 if you want to try it , it is an original old Amal , nearly new , so should have the right type of pilot jet . It was bought and fitted to a bike and the bike then sat in a shed for 30 years so no wear .

Brian ,

You won't get much response to a 24ME carburation question , most owners fitted a single carb , the twin set up was useless .

Yoy could try going up two to three sizes on the main jet and go from there .

Chris

[Brian Catt]

Chris, my question was in response to Colin's suggestion about only using 2 not 3 Concentrics.....
I was at Brill when Joe Johnson debuted the Cotton Starmaker. About 3 laps into practise, he pulled up where we were marshalling with the motor almost flat out. After persuading it to stop, we realised the carbs were loose and the fixed throttle control box was allowing the short cables to open the wick full hole. A bit of baling twine was applied to control things until he got back to the pits.
Good theory, useless in practice!!!!

[Dick F]

griffon gremlins

Thanks Rifleman for the information i am not sure what it was in the 900 range will contact Rob

[ADickerson]

Hi Dick, I seem to remember brother Rob saying that his 250 will bog down at low revs too, but otherwise goes really well. I'm also aware that on my 380 I'd been advised to fit a 20 Pilot jet. For sure it doesn't bog down but does need a good flooding to get started. both had 30mm Concentrics fitted. So from where I am(about two hundred miles away) you seem have a few choices:-
1. Leave it as it is, but change down early to keep it on the boil.
2. Fit a 20 pilot jet, but then struggle to get it started, the first time only!
3. Go on a diet

Good luck, look forward to seeing you up this way sometime.

[Rob]

The only thing I agree on 100% is put DD on a diet (and not one of buckets of curry followed by strawberries and ice cream - I am not joking!)

Anyway, this forum is for sensible discussion (??!!)

Getting back to the recalcitrant Griffon. For 3 years it ran fine then this fault developed. Something is wrong! As Dick says, it bogs down but it does this on first starting. Turn off fuel and eventually it clears but soon stops because the fuel is turned off! If you pull away gently it is reasonable until you give it a handful. It then sits there 4-stroking away again.

Ah, must be a carb fault. Check carb - exactly the right spec. Fit a spare Griffon carb, again, checked that it is a correct 930/3 - same problem. Fit another Griffon carb, same again. Take a spare float bowl and adjust fuel level to make it low - same again!

Had exactly the same with a Triumph Bonneville that ran excessively rich and had to be the carbs - 3 sets later (borrowed, not bought of course) and I concluded it must be something else. Correct! It turned out to be the Boyer ignition making it run rich.

Seems to be a theme here!

I am now going to dissect the ignition and timing-side oil seal in the unlikely event that it may be something in that region.

If that doesn't work, I shall revert to flower arranging and bonsai!

Did I ever tell you about the 1955 Norman B2S I had that ran on Corona limeade - absolutely true but another story as they say!

Griffoned of Horsham

[Phil Hyde]

Griffonitis

Have you checked the timing? Low speed spark? Doesn't sound like a carb problem.

[Dick F]

Griffon Gremlins

Rob has thought of going down that road Phil, thanks that may bear forth fruit,
I am sure he will not let it defeat him, he is now like a dog with a bone. regards Dicky

[Terry Sewell]

Griffon Carb

Tend to agree with Phil. I would advance the ignition and give it a try. Terry

[Rob]

Well,well!! Mr Brinkley, ex-Griffon rider appeared yesterday. Out came the Griffon for a demo of the problem. It started first kick, ran cleanly and went round the field ok with a comment from him that it sounded crisp!

AARGHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!

So what is it?? The only thing was that the bike had been standing in a red-hot poly tunnel. Could it have been a crankcase full of juice that had evaporated (never took the drain plug out before - whoops)?

Or, possibly some wiring softened and moved?

Mr Brinkley is convinced that he is a faith healer now!

I'll have another go at starting it soon now it is back in a cold shed!!

Baffled of Benfleet

[scott151]

Hi Rob,

I have had a similar problem to this on 2 occasions,

The first one was a faulty kill button after a very wet scramble, bike was fine at said wet scramble, was a sod at the next meeting, changed kill button all ok.

2nd occasion was a faulty ht coil under load.

I doubt you have carb probs as bike was fine before, I suspect that the spark is not strong enough to ignite the fuel under load.

Also ht plug cap my be arching

Good luck

Scott