Page 1 of 1

28 mm dellorto spit back

Posted: Tue Jul 14, 2015 3:45 am
by Scootermonkey
Just fitted a 28mm dellorto to a standard cast iron 200 Lambretta, along with a Scootopia clubman type exhaust. Main jets supplied with the carb were 110 and 105. Revs better with the 105 but seems to be spitting a lot of excess fuel out. Tried it with a remote filter and it seems to be flooding, but if I run this open mouth there's going to be fuel everywhere. Any ideas anyone?

Re: 28 mm dellorto spit back

Posted: Fri Aug 03, 2018 4:19 pm
by cgt75b
I have the same issue.

Re: 28 mm dellorto spit back

Posted: Fri Aug 03, 2018 5:09 pm
by Adam_Winstone
Open carbs spit fuel.

Reeds can/will help but it will still spit fuel.

If you don't want fuel everywhere then filtering is the only real option, however, there are plenty of options/arrangements for how you configure this... some of which will work well... but plenty that will not. Issues that you will need to address include:

- Carb mounted filter or remote filter.
- Hole in panel or no hole.
- Rubber mount or solid mount carb.
- Manifold type/angle/length.
- Filter size (and space available).
- Filter construction (single skinned foam, double skinned foam, foam density and/or paper cartridge type filter).
... you would also have the issue of airbox or remote but I note that you've already stated remote.

... or learn to live with fuel everywhere.

You'll be able to find most/all of these issues already covered in existing 'filter' threads, which typically generate lots of comments and opinions, so you may want to review those.

Good luck determining a solution that works for your requirement.

Adam

Re: 28 mm dellorto spit back

Posted: Sun Aug 05, 2018 9:38 am
by cgt75b
Hi Adam

Which remote filter would you recommend please mate?

Re: 28 mm dellorto spit back

Posted: Sun Aug 05, 2018 1:52 pm
by Adam_Winstone
Lots of people have their favourites, all which may have some merit, and I'm not different. My choice is the Breathe Sweet filter, which I've found does not restrict flow and performance, whereas the RAMAIR does, unless so large that it is very hard to accommodate under panels. However, I've found that I still need to machine manifolds shorter than most are supplied. I use the GP air hose, however, there are those who will tell you that this then restricts flow again. The new BGM air hose is a good option and I use this on one of my bikes. NB: I then use a 30 degree plumbers bend to fit the filter to the top of the hose, rather than bond it, which also turns the filter to fit nicely between a standard toolbox and tank.... a problem if you've changed to long range tank.

^... As this probably illustrates, you need to tailor a solution to suit your requirement. I've yet to see a dealer supplied carb + manifold + filer setup that I would be 100% happy with.

Re: 28 mm dellorto spit back

Posted: Thu Aug 09, 2018 11:06 am
by hat
A lot of spit back also suggests a rich setting but depends on how much you consider is a lot. I’m using the MB ‘tea strainer’ filter which has helped with my set up. The added benefit of this filter is that it doesn’t require any jetting adjustments

Re: 28 mm dellorto spit back

Posted: Fri Aug 10, 2018 5:22 am
by Minority
I'm surprised that nobody has commented on the fact that the 28mm carb is probably too big for a standard 200 cast barrel (even the Indian "stage four") and this won't help clean carburetion.

Re: 28 mm dellorto spit back

Posted: Sun Aug 12, 2018 8:40 am
by cgt75b
I have a 25 mil dellorto on a cast 230 and still massive amounts of spit back, how would you suggest rectifying this issue Minority?

Re: 28 mm dellorto spit back

Posted: Mon Aug 13, 2018 11:56 am
by Minority
cgt75b wrote:
Sun Aug 12, 2018 8:40 am
I have a 25 mil dellorto on a cast 230 and still massive amounts of spit back, how would you suggest rectifying this issue Minority?
That would depend entirely on what was causing the spitback in your case. As you mention It's a 230 It would suggest boring and stroking so you probably have "non Standard" port timings as a minimum difference to the "standard" 200 mentioned in the original post.