30mm dellorto flat spot

[Granty]

Troops, running an open mouthed 30mm dellorto with a 42mm clubman on a standard, stage 4 ish lump, main jet checked and is an 132.

Doing plug chops today and bike pulls really well through gears up to half throttle. plug a good chocolate colour so happy there.

The trouble is when I get to 3/4 throttle and above there is a big flat spot and the scoot seems to not want to rev out. Again done a plug chop and plug the same colour as before. Do you think the 132 main jet is a bit excessive or could it be the gearing? Comments welcome troops. thanks Grant.

[MickYork]

132 seems a bit big, try coming down to 120 and see how it performs........keep checking the plug though

[Granty]

132 seems a bit big, try coming down to 120 and see how it performs........keep checking the plug though

Thanks Mick - Looking at the jetting charts & looking at the plug -- its perfect (but too perfect) up to half throttle -- I wonder if there is a leaner atomiser in there and he's put a monster main jet in to compensate. Tomorrow morning is strip out day & I will report back to the Board.

It's as flat as a pancake at 3/4 throttle but pulls like feck through the gears up to half / 3/4 throttle. If I get it right this thing will be fast (even with me on it)

Have a good day Mick - G

[Granty]

OK troops -- this is what was in the 30mm delly after opening it up today

132 main jet
AV264 atomiser
X7 needle with clip 2nd top
55 pilot
70 choke
40 slide
running with a standard clubman on a 200 lump

Thoughts welcome? Im thinking of going with a AV266 atomiser and dropping the main jet down to 125 for a start

[hullygully]

Wouldn't the AV266 atomisor then be letting more fuel in??? Why dont you try the AS range that are slightly weaker than the AV

[Granty]

Thanks for the feedback -- I normally drive at just over 3/4 throttle and I hope that a smaller main jet and larger atomiser will reduce or irradiate the flat spot at that point where the main jet takes over.

The majority of jetting charts ive seen online or on different forms are using AV atomisers -- I'll report back with an update when the jets arrive -- G

[Granty]

Made the changes so now running
standard clubman on a 200 lump
30mm Delly - Open Mouthed
125 main jet
AV266 atomiser
X7 needle with clip 2nd top
55 pilot
70 choke
40 slide

Bit boggy just below 1/2 throttle but manageable -- plug a good colour
Opened up to 3/4 throttle for 1/2 mile and no flat spot -- didn't have enough time to plug chop it so maybe the morn night for that.

lets see if I can now keep the carb rubber on & stop it popping off!

[Rich Oswald]

Just my opinion but your main and pilots look too big. I would think about 120 main and 50 pilot would be about right for a st'd 200,

Rich'

[Granty]

Just my opinion but your main and pilots look too big. I would think about 120 main and 50 pilot would be about right for a st'd 200,

Rich'

Thanks for the input Rich -- I'll get out this weekend for a blast and check out this main jet - G

[Granty]

Troops -- seem to have taken out the obvious flat spot now, just looking at the finer details, pulls really well up through the throttle stages -- now running

30mm Delly - Open Mouthed
42mm AF Clubman
2 1/2 turns out
50 pilot
70 choke
40 slide
AV266 atomiser
X7 needle with clip 2nd top
125 main jet

Is a little lumpy idling so maybe thinking a 1/2 turn in with the mixture screw so only 2 turns out.

What a school day has turned out to be --

[Granty]

Just my opinion but your main and pilots look too big. I would think about 120 main and 50 pilot would be about right for a st'd 200,

Rich'

Rich -- Ypu're not going to be far away -- changed to a 50 Pilot and tick over is much improved -- up to 1/2 throttle is bang on but still too rich 3/4 throttle up with a 125. working my way down now -- thanks for your help with this - G

[Granty]

Troops -- eventually got the carb set up & ready to go for real, the last bit of advice sounds a bit dumb but I've only ever had smaller carbs running through the box, I now have a opportunity to try out a 20mm open mouth carb -- quick question.................... is there any difference in driving an 30mm open mouth throttle wise then a 26mm through the box, particularly on using the throttle ie gradual opening up etc?

Cheers Troops - G

[Rich Oswald]

Troops -- eventually got the carb set up & ready to go for real, the last bit of advice sounds a bit dumb but I've only ever had smaller carbs running through the box, I now have a opportunity to try out a 20mm open mouth carb -- quick question.................... is there any difference in driving an 30mm open mouth throttle wise then a 26mm through the box, particularly on using the throttle ie gradual opening up etc?

Cheers Troops - G

I would say no to this question unless of course you have a highly tuned kit like a TS1 or RB etc where the power band can kick in quite soon in the throttle opening.

Rich'

[Warkton Tornado No.1]

Hi.

Sorry to have joined this thread so late. Your initial set-up was:

132 main jet
AV264 atomiser
X7 needle with clip 2nd top
55 pilot
70 choke
40 slide

For what it’s worth, going back to your original set up, & advocating one change @ a time, I’d have tried lifting the needle one or two clips whilst keeping the AV264. Then tried dropping the main jet down to 125 or so.

My reasoning is that the bottom end was so nearly right with the AV264 & 132 sounds too big.

However, don't be surprised if you end up with a 45 slide.

[Granty]

Troops -- eventually got the carb set up & ready to go for real, the last bit of advice sounds a bit dumb but I've only ever had smaller carbs running through the box, I now have a opportunity to try out a 20mm open mouth carb -- quick question.................... is there any difference in driving an 30mm open mouth throttle wise then a 26mm through the box, particularly on using the throttle ie gradual opening up etc?

Cheers Troops - G

I would say no to this question unless of course you have a highly tuned kit like a TS1 or RB etc where the power band can kick in quite soon in the throttle opening.

Rich'

Thanks Rich -- just wasn't sure what the craic would be, its a stage 4 200 lump, nothing mega