Scooterotica

I have been trying to tune my Lammy for going on two years now, with limited success. I am coming to the realization that the carburetor is the problem--a Delly PHBH28. Here's my setup:

SIL GP200 cases and ignition system
Timing at 19-degrees
Tameni crankshaft
Rapido225 with matching head
Ports and transfers matched and polished
Vertex piston
Squish at 1.4mm, no gasket
MB Developments inlet manifold and matching rubber adapter
JL1 exhaust
SX200 gearbox
16/47 primary gears

Current carb setup is 125 main, 53 pilot, AV266 atomizer, X4 needle. I don't know what throttle slide is in--whatever the carb came with.

The problem is that the EGT gauge spikes to 1200F quickly in the 25-50% throttle range, no matter what gear and revs.

I hear mention of Dell'Orto VHSx carburetors, although I know nothing of them. They aren't widely used here in the States. Mikuni TMXs are popular here.

Any recommendations based on my setup? I want this bike to be a fast touring bike.

A reply from a previous post asked:

"52 idle
AV266 atomiser
X13 needle
118/120 main"

I have tried those jets but not that needle. According to my chart, the difference between the X4 and the X13 is the X13 is fatter (2.5 vs 2.48) and the taper is longer. A skinnier needle would seem better in this circumstance. I don't know what a longer taper would result in.

To address another question, the engine is recently rebuilt and tight: New bearings and seals throughout, all clearances to spec, including 0.35 bore.

I am wondering if a PHBH just won't do the job and something else would be more appropriate. I'm tired of chasing this problem.

if your barrel was 1200 degrees mate, it would be a blob of metal falling out the bottom of your scooter! try another carb , and forget the digital high tech b@11@x thats got everyone paranoid. junk the gizmo"s, and buy some jets.... have a play about and do it "seat of the pants" . you"d think we all were riding 200bhp superbikes! these EGT"s /dynos/ and all the other shite thats knocking about are probly responsible for more f@@ked barrels than anything else. ive had three in the last two weeks phone me "had my scooter dynoed, blew up on the way home"........ £100 quid to swap two carb jets, turn a mixture screw, and say"take it easy on the way home". money for nowt. snake oil.........

Could try a different needle, the upper part of the tapered needle should influence the carb at this point, pick a needle with similar dimensions But slightly narrower at the thickest point, or a needle thats the same length and has similar dimensions as the one your using but where the taper starts sooner this should also richen the mixture a little at low to mid revs....then fine tune by changing needle jets if needed.....This is how I jetted My GP when I had the Rapido race fitted with the Dellorto flat slide.... the Kit was just released and no one had jetting details for me to pick from.... not even Ray Kemp... and my TS1 settings were way out....I think I endedup on a K8 needle and a 265 or 266 I tried four or five different needles before the K8.... Its a needle Martin Cooke somtimes put into TS1's, which I had bought for mine but was a little too weak on mine but it worked ok on the Rapido....not saying this is going to fix it, its just a little input to let you know your not alone...... I feel your pain...

Thanks for the input. I'll disagree on the 1200F comment, though. Because the exhaust gas is measuring 1200 doesn't mean the metal is. Doing it the old school way, seat of the pants, has gotten me two rebuilds so far. I'll opt for the gizmos this time around, thankyouverymuch!

Is the consensus that a PHBH is a good, workable carb?

just to clarify.........
do you run carb open or filtered..........?
and we really would like to know what slide you have in there......obviously the slide and its cutaway.......affects the things in the rev range you are having probs with...............
i would have thought you would need a 40 slide............
but what have you got..........?

goldeneye wrote:if your barrel was 1200 degrees mate, it would be a blob of metal falling out the bottom of your scooter! try another carb , and forget the digital high tech b@11@x thats got everyone paranoid. junk the gizmo"s, and buy some jets.... have a play about and do it "seat of the pants" . you"d think we all were riding 200bhp superbikes! these EGT"s /dynos/ and all the other shite thats knocking about are probly responsible for more f@@ked barrels than anything else. ive had three in the last two weeks phone me "had my scooter dynoed, blew up on the way home"........ £100 quid to swap two carb jets, turn a mixture screw, and say"take it easy on the way home". money for nowt. snake oil.........

What a load of s**t.

No...we are not riding 200bhp superbikes, however.....it is absolutely amazing how many scooter owners are riding around on 40 year old scooters, thinking everythng is fine, when in fact it is clearly NOT fine. Clutches dragging and slipping, kickstarts grinding, oil leaking, cylinders pinking, mid-range lean spots that they roll into after a high speed blat, reed valves on non-reed valve engine, gearing and exhausts that dont match, shot oil seals, f@@ked bearings, lean jets, rich jets, electrical faults, split air hoses.....the list goes on. .

As for CHT and EGT gauges.......can they stop and f@@ked scoot blowing up...? Of course not, but can they help someone who is tech-savvy watch his engine for problems and prevent a disaster...YES THEY BLOODY CAN!

And please......Dyno? Snake oil? These EGTs/dynos and other 'gizmos' as you put it are not the problem....

Blame the garage for being rip-off merchants, blame the operator for being s**t, blame the customer for not listening to the full story and only wanting more BHP, blame what you want.....but dont say a dyno is snake oil.........its a bloody good tool for measuring power curves, monitoring performance gains, checking rich/lean spots throughout the rev range, and helping a decent bike/scooter mechanic get a customers scooter where they want it....be it more powerful, safer to tour on....or both. Dynos and EGTs dont f@@k peoples scooters up, s**t mechanics do....as do unsuspeccting scooter owners, and negligant scooter owners.

Dont slag off the equipment, think about the problem....the cause, and the solution...and what/how equipment can help.

DaveInPortland wrote:I have been trying to tune my Lammy for going on two years now, with limited success......

......I don't know what throttle slide is in--whatever the carb came with.....

You might want to find out, two years of carb problems is a long time not to bother checking, it might make things a whole lot easier if you had a look.

not bad that dan,thinking the same thoughts!
regards
joe

drunkmunkey6969 wrote:

goldeneye wrote:if your barrel was 1200 degrees mate, it would be a blob of metal falling out the bottom of your scooter! try another carb , and forget the digital high tech b@11@x thats got everyone paranoid. junk the gizmo"s, and buy some jets.... have a play about and do it "seat of the pants" . you"d think we all were riding 200bhp superbikes! these EGT"s /dynos/ and all the other shite thats knocking about are probly responsible for more f@@ked barrels than anything else. ive had three in the last two weeks phone me "had my scooter dynoed, blew up on the way home"........ £100 quid to swap two carb jets, turn a mixture screw, and say"take it easy on the way home". money for nowt. snake oil.........

What a load of s**t.

No...we are not riding 200bhp superbikes, however.....it is absolutely amazing how many scooter owners are riding around on 40 year old scooters, thinking everythng is fine, when in fact it is clearly NOT fine. Clutches dragging and slipping, kickstarts grinding, oil leaking, cylinders pinking, mid-range lean spots that they roll into after a high speed blat, reed valves on non-reed valve engine, gearing and exhausts that dont match, shot oil seals, f@@ked bearings, lean jets, rich jets, electrical faults, split air hoses.....the list goes on. .

As for CHT and EGT gauges.......can they stop and f@@ked scoot blowing up...? Of course not, but can they help someone who is tech-savvy watch his engine for problems and prevent a disaster...YES THEY BLOODY CAN!

And please......Dyno? Snake oil? These EGTs/dynos and other 'gizmos' as you put it are not the problem....

Blame the garage for being rip-off merchants, blame the operator for being s**t, blame the customer for not listening to the full story and only wanting more BHP, blame what you want.....but dont say a dyno is snake oil.........its a bloody good tool for measuring power curves, monitoring performance gains, checking rich/lean spots throughout the rev range, and helping a decent bike/scooter mechanic get a customers scooter where they want it....be it more powerful, safer to tour on....or both. Dynos and EGTs dont f@@k peoples scooters up, s**t mechanics do....as do unsuspeccting scooter owners, and negligant scooter owners.

Dont slag off the equipment, think about the problem....the cause, and the solution...and what/how equipment can help.

I think your the one who's being a bit touchy,these dyno's are only as good as the man on the end of the knobs ,i -we've all heard of many stories of scooters seizing on the way home from being dynoed ,i'm afraid you can't be totaly unbiased when you have invested time and money in a dyno your self.

teamv wrote:i'm afraid you can't be totaly unbiased when you have invested time and money in a dyno your self.

Not trying to be unbiased......trying to be pragmatic.