Hi Guy's
I have a friend that's recently purchased a SER 3 125 Special with a 175 head etc.....and it has a jetex 22ml carb!! I know there has been much said about these carbs but not sure about it on his set up as its a right "bugger" to get it ticking over nicely and when its running when you change gear either up / down it seems to race like Mary hell, so no drop in revs at all. I have checked the throttle cable and that's all fine nice and free etc.
So I suppose what I am asking is there a better carb that would be better for this set up...as the air and fuel mix seems to be at loggerheads, and would a fast flow fuel tap help as well?
Cheers
Carb Suggestions
-
Adam_Winstone
- registered user
- Posts: 1693
- Joined: Tue Jan 31, 2012 8:54 pm
- Main scooter: Lambretta GP
- Contact:
Fast flow tap is a good addition to ANY Lambretta as it ensures that the carb gets at least enough to avoid fuel starvation.
Some Jetex give issues, others require very odd jetting combinations (i.e. some that should be way too rich but actually perform as though correctly jetted), the Jetex jets and other carb internal (atomiser, float needle, slide, etc) are very 'hit and miss' in manufacture and the results that they give... particularly the jets (replace with genuine Dellorto), HOWEVER, most of them are perfectly good when jetted correctly for your motor's individual needs. Many people have excellent service from their Jetex carbs and the 22mm size does sound ideal for your 175 motor.
Also, please note that EVERY/ANY carb needs to be jetted to a specific motor's requirements and I have NEVER once found a pre-jetted carb to be perfectly jetted for the motor that you ask for it to be pre-jetted for. Indeed, I've bought some very expensive carbs that have supposedly been pre-jetted for very common engine configurations, only to find that they are miles out, which in turn has required that I spend hundreds more on carb parts so that I could set it up correctly!
I've also known mates to sell perfectly good carbs that they were having issue setting up (their fault rather than the carb's), only then to buy even worse replacement carbs that were not set up correctly... but worse still, had faults in the manufacture that required the carb body to be drilled out to avoid fuel starvation!!! Out of the frying pan and into the fire comes to mind.
If you are not good with carbs then I'd suggest you take the bike to someone that is. Yes, you may spend a lot of money to get it right but I don't see the 'buy another carb roulette' as a better option.
Best of luck with it.
Adam
Some Jetex give issues, others require very odd jetting combinations (i.e. some that should be way too rich but actually perform as though correctly jetted), the Jetex jets and other carb internal (atomiser, float needle, slide, etc) are very 'hit and miss' in manufacture and the results that they give... particularly the jets (replace with genuine Dellorto), HOWEVER, most of them are perfectly good when jetted correctly for your motor's individual needs. Many people have excellent service from their Jetex carbs and the 22mm size does sound ideal for your 175 motor.
Also, please note that EVERY/ANY carb needs to be jetted to a specific motor's requirements and I have NEVER once found a pre-jetted carb to be perfectly jetted for the motor that you ask for it to be pre-jetted for. Indeed, I've bought some very expensive carbs that have supposedly been pre-jetted for very common engine configurations, only to find that they are miles out, which in turn has required that I spend hundreds more on carb parts so that I could set it up correctly!
I've also known mates to sell perfectly good carbs that they were having issue setting up (their fault rather than the carb's), only then to buy even worse replacement carbs that were not set up correctly... but worse still, had faults in the manufacture that required the carb body to be drilled out to avoid fuel starvation!!! Out of the frying pan and into the fire comes to mind.If you are not good with carbs then I'd suggest you take the bike to someone that is. Yes, you may spend a lot of money to get it right but I don't see the 'buy another carb roulette' as a better option.
Best of luck with it.
Adam
-
Adam_Winstone
- registered user
- Posts: 1693
- Joined: Tue Jan 31, 2012 8:54 pm
- Main scooter: Lambretta GP
- Contact:
PS - If you are not familiar with the inside of this engine then the problem may well be caused by other factors, e.g. bore wear, air leaks, fuel starvation from tank to carb, ignition issues, etc.
Cheers thanks for that....but I have changed the jets already on the jetex carb. I think there may well be another issue somewhere...not doubt find it to be something least expected!!!! 
Air leak somewhere with you saying it revs like mad??
Mmmmm,that's what I am thinking. Not 100% sure where really neither. His whole system around the carb /air filter box etc was rather, whats the word I am looking for "airy"?...... I have made that all best I can so that is why I am unsure what it could really be....but it races like anything when you want to throttle down to change gear .....any how thanks for your reply
-
Adam_Winstone
- registered user
- Posts: 1693
- Joined: Tue Jan 31, 2012 8:54 pm
- Main scooter: Lambretta GP
- Contact:
^... that's why I think that you should investigate further before buying another carb. If it turns out that it is carb related then a new carb might be in order, I just didn't want you to rush out and buy one.
Is it a standard 22mm Jetex or does it look to have been bored to a bigger size (e.g. 25 or 26mm)? I ask as a bad job here can lead to air leaking around the slide and causing the motor to rev.
Adam
Is it a standard 22mm Jetex or does it look to have been bored to a bigger size (e.g. 25 or 26mm)? I ask as a bad job here can lead to air leaking around the slide and causing the motor to rev.
Adam
Hi...Yeah, it is a standard 22ml jetex...when I took the carb apart to look it had no gaskets!!! so bought those as I thought that was why...but no.
Its all interesting stuff getting to the bottom of the why's and wherefore's I will continue to investigate, maybe more questions to follow
Thanks for your help guy's
Its all interesting stuff getting to the bottom of the why's and wherefore's I will continue to investigate, maybe more questions to follow
Thanks for your help guy's