Jump to content

CV Carb mod to replace plastic washers, which locate under needle circlip that wear out.


Recommended Posts

Hi, finally I managed to play around with my carbs.

Since I am trying to find a simple solution I played with the parts I have.

What I did was to sand down the old spacer and placed this in the low part of the slide.

Then fitted a new plastic spacer on the needle and voila.

It me not be perfect but the result is (y)




Edited by minipower
Link to comment
1 hour ago, jonny1bump said:

So cheapest I can see new plastics is 5 euro each plus postage.

Now you got two pieces of plastic that wear out. 

Makes no sense what so ever, when you can have all in one design that dont wear out cheaper.

If you go on alphasports website, it gives the same part number for 36's and 40's needle seats. Can't be right as the seats on the 40's are way bigger in diameter than the ones found in the 36's.O.o So even ordering the right ones might be an issue. 

As for plastic, after pulling out the needles from a set of 11 M carbs and seeing the wear I thought ally ones couldn't do any worse damage so what the Hell?  


Link to comment
  • 5 months later...

Hi again

I said I'd do a follow-up when I fitted the spacer things for real, so here goes.

These are going in a set of 38s from a GSXR 750, M I think,  the power jet ones.

They have a Dyno-jet kit in them (don't all start hating, didn't know about the other kits available at the time) & they have been set up on a dyno for fine tuning.

So to start with I measured the standard height / lean.



Pretty bad that.

Quick shot to show how they compare up.



However, when I fitted them in, the needle didn't stick out the same.


Bit strange, had a look down the slide bit & could see the issue, stop me if I'm getting to technical.

When I fitted the kit, I remembered that you have to block one of the slide 'air holes' & there was a bit of the glue / Araldite sticking up into the slide.





Couldn't clean that up in there, so, filled a bit off the spacer &, Bob's your uncle, jobs a good-un.



Result ended up like this.



Same height & straight up.

Then I started to get a bit mad, extra weight affecting slide speed, affecting performance, blar blar blar.

Glad to report, still runs sweet as with no noticeable effect anywhere.

Also started to get a bit paranoid about water in the tank. I've had it 10 years & never emptied it or checked it, It does get used all year round but less so if it's freezing or snowing, I'm not fecking crazy.

However nothing to worry about, the last dreggs clean as the day Mr Tesco sucked it out of the ground. Too much time listening to Face-slap.



Hope this makes sense, great fix.






  • Like 1
Link to comment
  • 3 weeks later...

Rebuilt set Bandit Mk1 carbs other day and forgot how they look inside. Interestingly suzuk changed design completely to hold needle square and to stop needle holder wearing out. Thought share couple of pics of bandit set up.

This back up my line of thinking with the gsxr mod.




Link to comment

did you ever get anyone to cnc them?, only reason i ask is i have a cnc sitting idle at the moment, and about 30 years of programming the fking thing!

i had a quick look at the drawing, and they are a piece of piss to make, but difficult to hold, i have got an idea to batch them at maybe 100 at a time

my business is closed at the moment, and as i am self employed i am not sure when we will re-open, the m/c is sat there idle,

i am not touting for work as i can afford the downtime, but if i can help out oss members.......

i am not going to make just 4 except as a sample, but if there is enough to be worthwhile, i can make them no problem, stainless, aluminimum, titanium, take your pick

  • Like 1
Link to comment
  • 1 month later...
  • 3 weeks later...

Got to add some fairly recent findings on this subject.

I had my spacers  shaped like minipower's  (and variants of) before I bought Jon's spacers. I thought my needle jets were fine and initially my low/mid-range was rich with the new ally spacers - I milled .8mm off the spacers and got a good set-up ….. but this year whilst working on my needle tapers etc, it was obvious something wasn't right - turns out that 2 of the needle jets were pretty worn and the other 2 weren't in great shape. It's very easy to not notice the wear, they look fairly round, but they don't meter the fuel very well - especially if you increase inlet velocity with a big bore and flow work. Now with in spec needle jets, my own needles and Jon's spacers I have massive mid-range and perfect manners at idle and cruise. With standard spacers or modified ones, the needle jets will wear - I reckon my must've taken a few thousand miles before causing problems. The standard set-up is shite ! the needle either leans against the leading edge or wobbles about. 

Looking back I should checked the needle jets more thoroughly - I wasted so much time chasing my tail !

  • Like 1
Link to comment
  • 1 year later...
On 11/28/2018 at 11:32 AM, CockneyRick said:

This is in no way a criticism, just an observation that i have passed on to @jonny1bump

I have fitted these to my BS38's & before, needle protrusion was at 61mm with clip in middle of 5.

After fitting, the protrusion was down to 59mm. So i raised clip to top notch of 5 & needle then protruded 61mm again.


My point was, has anyone had this when they fitted, or as J1 suggests, they were made the right thickness to stop this happening?

I will strip mine down again & double check it all, but chances of all 4 not seating correctly is remote. I can only think the step in 38's isn't as deep? 

Only way of really knowing would be to cut the slide apart, if my depth gauge won't fit :) 

Just going back through this thread, im running 38s on my 1127 with the factory pro kit, iv had some richness around the 2500-4000 rpm range, iv had to put the clips to the top lowering the needles fully. the recommendation from factory pro was clip position 2 , im now in position 1 the top and its running great now. 

  • Like 1
Link to comment
  • 2 months later...
  • 3 months later...
  • 7 months later...
  • 1 year later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...