weber what if ?

[Andrew2]

CLR and Marine clean also work well

I tried CLR Higgy but did'nt get a result unfortunately.I'll look for some Marine Clean.Is this the stuff your talking about?.

http://ppcco.com.au/preparation_marineclean.htm

It sounds a bit like Prepsol/Prepwash.

Cheers
Andrew

[higgy]

yup thats it

[jayh]

Tried a lot of combinations of jetting while I've been waiting for my new pump cams to arrive.
Jfiore's combination of 60 idle 165 mains and 185 Air correctors,is a very nice combination,more responsive up top than the combination of 170 mains and 185 air correctors that I was using .With no pump shot, the 60 idles can be used to cover the lean hole rather than the 170 mains (which were a tad rich on hard accelerations).It would be too rich normally for the 60 idles with the stock pump cam,but they are a very nice alternative once it has been modified .The only negative that I noticed was a little popping out of the exhaust on the overrun once hot,but this may be because I have my float set a little higher than normal.Another possibility would be to drop down to a 59 idle and see if that helps .If this causes the lean hole to reappear a 166-167 main could be fitted to cover it again.
It's going to be very interesting to see how the whole setup works with a more suitable pump cam profile,and a bit more fine tuning,it's VERY close to perfect now !!.

It appears at this stage that a .35 mm hole,bleeds enough fuel back to the float chamber to avoid any rich spots on slow throttle openings,but still allows enough fuel to stop hesitations on fast openings.
This of course has to be matched to the cam profile,which I currently have set up with a similar to stock profile,but I still had to take a little off the start of the cam,to overcome the stumble in 1st and 2nd when taking off and I didn't have enough cam or araldite left to get an exact copy done of stock.

This project has gone full circle,and is getting back to near stock jetting,which should allay the fears of any that were worried about running their bikes lean,any modifications done to the pump cam side of things only last for a second or so during actual operation and therefore can have no damaging effects on the engine,and will only be felt as performance increases or decreases that last for that small fraction of time, ie.the first and second gear rich bog,which extends into 3rd 4th and 5th gears as a low rpm lack of torque.This should not be confused with the lean stumble at higher rpm,they are seperate issues

The key to solving the problem in hindsight appears to have been to totally eliminate the accelerator pump ,then tune the carby as per normal procedures,then reintroduce the pump shot,taking note of where it is detrimental to operation,then try to perfect those areas of pump operation.Ain't hindsight a wonderful thing. J.

[higgy]

The key to solving the problem in hindsight appears to have been to totally eliminate the accelerator pump ,then tune the carby as per normal procedures,then reintroduce the pump shot,taking note of where it is detrimental to operation,then try to perfect those areas of pump operation.Ain't hindsight a wonderful thing. J.

That was my original thinking and why I decided to do the pump circuit last.

Your experiments have certainly helped the overall understanding of the DCNF

I'm thinking once I get my stator situation sorted and the 906 back up and running I'll go your route and see where it leads...............

[jayh]

I know I mentioned this in an earlier thread but the importance of it has really only just hit home with me,so I'll say it again.It is critical to the proper operation of the weber (and easy to do).

The idle speed adjustment screw setting is critical to a smooth operating bike.

When you have it right,the bike will smoothly slow down at intersections etc. and there will be no slack spot off of idle as you reapply the throttle,just as smooth on acceleration.

Today I switched back down to the 57 idles to try them in comparison to the 60 idles which were really smooth from take off and on deceleration but were causing some popping in the exhaust on the over-run and all of a sudden the slack spot off idle reappeared,as well as what appeared to be either a slight rich or lean miss.

The bike was behaving like a pig again,lots of compression braking (way too much) and I had to guess where the power was going to start again on acceleration.

This had me scratching my head,as I hadn't changed the pump cam or played with any settings except idle mixture,and that didn't seem to fix it no matter how much I adjusted it.

I remembered that the weber manuals say that a lean spot off idle can be caused by incorrect adjustment of the idle speed screw,and I had adjusted it when I fitted the 60 idles so I thought I'd have a play with that..........

Well a lean spot isn't a very good description of how it effects the operation of the engine,so I'll try and explain how it effects the operation of the paso.

If you have the screw wound in too far,when you rev the engine it will take a while to return to idle - this effects your compression braking,so too far in and the bike wants to run on into corners...not nice.

if you have the screw wound out to far,the engine snaps back to idle,you would think that this is a good thing but it is not as it jerks when compression braking and creates a slack spot,when you go to accelerate again.....extremely uncomfortable mid corner.

To get it just right so you have nice smooth compression braking and no sudden throttle when reapplying,do the following :

Most importantly-take your bike for a decent ride and get it FULLY WARMED UP.

Roughly set your idle mixtures - now wind the speed adjuster in 1/2 turn so that when you rev the engine it takes a while to return to idle.Slowly adjust the screw back out bit by bit with a rev each time until the engine just returns to idle normally- NO MORE !.Re do your idle mixtures and redo the above if necessary.Go for a ride and do any fine tuning based on how it rides...running on during deceleration,back the screw out slightly.A slack spot on acceleration-turn it in slightly.There is a just right position for each size idle jet !

You should find the bike much more user friendly when set like this,no more of the chain snatching as you go on and off the power,just nice and smooth delivery,as well as easier blipping of the throttle and downshifting,it makes a huge difference ! J.

[jayh]

A quick update.After a couple of months of trials I went away from the fuel bleed idea and blocked the hole up again.Instead I decided to revisit my jetting combinations,which had remained basically unchanged since the modified pump cam solved most of my tuning issues.

without the extra fuel from the cam,I was able to increase the size of my idle jets,with none of the rich problems from my earlier trials.The following are idle jet sizes,with a minumum main jet size to stop the lean hole.My float level has been raised by 2mm from stock,to promote earlier starting of the main jets.An increase of air correctors above 185 seems to lean the mixture down and cause problems,but my next size up was 200,so maybe 190 or 195 could be tried.These will hopefully be more usefull here than scribbled on my shed wall .My new cam has a 10mm delay at start,and then a constant gradient with a rise of about 4mm,this is not critical though.Cams are available from webcon,their link is mentioned earlier on this thread and are easily modified.

IDLE MAIN AC
55 170 185 maybe 190 ac? Hot climate sea level above 30C
56 165 185 Mild climate sea level 5-30C
57 160 170 close to stock,perhaps try raising float by 2mm first.

I am now running the 56,165,185 modified cam combo and my bike has never run better,slight hesitation while warming up ,but once warm perfect ! J.

[Brutus]

Jay,
I've read this post a couple of times to understand how the weber works. Ordered the combo 56, 165 main and 185 ac. Also got two alu cams which have to be altered if I'm not mistaken. Only thing is that I don't understand what you are running now.. The stock cam that you have altered 10mm at start (flat)? Or you're still using the alu cam with 6mm of nothing, till 10.3mm little ramp, flat till 16mm and the rest uphill? Can you post a pic of the latest cam..? Many thanks for all the effort. Got my bike running again today with the new setup. Running the new alu cam (not altered yet) and it is spitting as hell. Cold engine and didn't take it for a run though. Btw I spend a couple of hours on sanding and polishing the internal of the weber, intakes to the engine and tuning of the heads. Got it all shiny and smooth . Will see what happens when I got the cam right.
Léon

[Brutus]

couple of pictures:

[stylianos62]

......perfect weber really.
I must clean my own like yours,......bravo.
Good summer.

[jayh]

PM sent.You have that weber really looking good !,and writing the service details on the rocker covers is a great idea,especially if you have one or two shims that were getting close to service specs ,(like a couple of mine),you can go straight to them for a quick check.I'm going to do the same next time. J

[higgy]

The weber when setup properly will rock you..It works so much better then the early FI on the 907 regardless of whose chip you use Only DI will work better let the flames begin

[paso750]

Btw I spend a couple of hours on sanding and polishing the internal of the weber, intakes to the engine and tuning of the heads. Got it all shiny and smooth .

That`s exactly what you don`t want. The carb manifolds need a slightly rough surface. Polishing may increase air speed but reduce the turbulances which are required for a good air/fuel mixture. So a surface that`s too rough is no good and one that`s too smooth neither. If you polished smooth I`d go over it with sandpaper and roughen it up again.
More important than trying to polish these things is to make sure the paper and rubber gaskets don`t stand over 1-2mm as they often do and that the transitions of carb to mounting plate, mounting plate to inlet manifolds, inlet manifolds to cylinder heads etc are smooth.

G.

[higgy]

Btw I spend a couple of hours on sanding and polishing the internal of the weber, intakes to the engine and tuning of the heads. Got it all shiny and smooth .

That`s exactly what you don`t want. The carb manifolds need a slightly rough surface. Polishing may increase air speed but reduce the turbulances which are required for a good air/fuel mixture. So a surface that`s too rough is no good and one that`s too smooth neither. If you polished smooth I`d go over it with sandpaper and roughen it up again.
More important than trying to polish these things is to make sure the paper and rubber gaskets don`t stand over 1-2mm as they often do and that the transitions of carb to mounting plate, mounting plate to inlet manifolds, inlet manifolds to cylinder heads etc are smooth.

G.

Well sorta. Smooth is good,shiny is irrelevant. The mixing of fuel and air is a complicated subject. Atomization of the fuel has more to do with temp and pressure changes than anything else. But then you need to get the most air flowing as possible with the least amount of turbulance from shock waves as possible. Shock waves cause the fuel to stratify which generally is bad for combustion but can be useful at a particular rpm

My head is starting to hurt


Shiney like a trumpet before the fuel is introduced is generally considered to be a good thing. After the fuel is introduced smooth as in a minimum of obstructions to air flow and straight is more useful. Rough is bad

[Brutus]

Shiney like a trumpet before the fuel is introduced is generally considered to be a good thing. After the fuel is introduced smooth as in a minimum of obstructions to air flow and straight is more useful. Rough is bad

Tx. Thats what I was trying to achieve. I noticed that for example the stock manifolds had rough edges and some obstacles from casting. Grinded this all down and got it smooth enough. The venturi, tubes and upper part of the weber is close to "mirror-polished". Also set the floatlevel to 45mm (without gasket) and the pump cam altered. Got some pictures and a link to youtube of how the bike is running now. Allmost there thanks to the input of this forum, esp Jay. One thing I noticed is that I had to unscrew the idle mixture screw then before. Had to give it allmost 4 x 360 degrees outwards. I still have to testride it, but currently without rear shock. It's an öhlins that needs some work. I'll make a new topic of that..









http://www.youtube.com/watch?v=GEAG6qsZQls

[higgy]

Sounds like you need a valve adjustment and a new spring for your sprag while you are at it. 4x is too much adjust your idle jet