revtothelimit - motorbike forum

Allens used to be the people for all things carbs, but a quick Google suggests they've gone out of business.

Seems like your bike has CV carbs, so it's the return springs you'd need to be looking at to reduce pull weight. There is a spring on the slide, but it's related to how much vacuum it takes to open the carb, you wouldn't want to mess with that.

Unless it's a known issue for the model, you might first want to make sure the linkage between the two carbs is free and lubricated, ditto the cable(s) and butterfly shafts. I've even had a tight throttle due to rust forming on the handlebar under the twist grip.

A_morti wrote: Sun May 17, 2026 4:37 pm Seems like your bike has CV carbs, so it's the return springs you'd need to be looking at to reduce pull weight. There is a spring on the slide, but it's related to how much vacuum it takes to open the carb, you wouldn't want to mess with that.

Unless it's a known issue for the model, you might first want to make sure the linkage between the two carbs is free and lubricated, ditto the cable(s) and butterfly shafts. I've even had a tight throttle due to rust forming on the handlebar under the twist grip.

Thanks but it's definitely the slide springs I want. Dynojet have never made a kit for the VT250 AFAIK and so I've got to find another source. The return springs on the throttle quadrant are fine. I've got the kit to measure/adjust/correct, just need the springs.

Once I've got lighter springs I can open up the main jets slightly to match the semi-open pipes.

cmsnl.com show the spring part number as 16050KE8004

https://www.cmsnl.com/honda-vt250f-1982 ... 050ke8004/

I can't see all the other Hondas that use the same part number without registering, but the VF and VT500 use the same spring.

Do Dynojet make springs for the 500s?

I fitted a 650 Hawk Dynojet kit to my 400 Bros (using the smallest size jets in the kit) with the springs and the slide drilled. It went like stink (comparatively).

KungFooBob wrote: Sun May 17, 2026 6:27 pm cmsnl.com show the spring part number as 16050KE8004

https://www.cmsnl.com/honda-vt250f-1982 ... 050ke8004/

I can't see all the other Hondas that use the same part number without registering, but the VF and VT500 use the same spring.

Ah, but it's a lighter spring I need!

What will lighter springs achieve?

I know the DJ springs made a massive difference on my 98 Fireblade, the throttle response was so much snappier, but I assumed they were heavier springs to help close the slides quicker?

Or does lighter springs mean there's less vacuum needed to lift the slides?

KungFooBob wrote: Sun May 17, 2026 6:38 pm What will lighter springs achieve?

I know the DJ springs made a massive difference on my 98 Fireblade, the throttle response was so much snappier, but I assumed they were heavier springs to help close the slides quicker?

Or does lighter springs mean there's less vacuum needed to lift the slides?

It's the whole set-up I want to change..... The bike has semi-open pipes but standard air filter and carb settings, that's no good. Dynojet used to make (probably still do) carb kits for most common models of UK bikes, but they never made a kit for the VT250.

The kit comprises different slide needles with a more tapered profile, lighter slide springs and a choice of larger main jets. I can re-profile the needles and I've got a set of jet drills, but I can't find a source for lighter springs.

Once done, the bike will breathe better and be happier in general.

CV carbs all have the same inherent issue - they slow throttle response (to different degrees). Lighter springs means less vacuum is required to lift the slide but the whole system has to work together - right spring weight/jet size and needle profile. The result is much snappier throttle response and an engine that just runs a little bit happier. The ultimate problem with CV carbs is that if the engine is tuned properly then the inlets are sucking so hard that the slides start to rise, even at tickover. You end-up with a bike that holds-up everywhere and then it's time to fit flatslides, which are a different ballgame and better in every way.

All I'm aiming to do though is set the carbs up to run properly with open pipes.

Bit more progress today - the BT46s arrived so I fitted those which was a complete PITA - especially the front as it's only a 16in rim and there's no room to work. Anyway they seem a good profile and are light years younger than the road Runners!

Also changed the front pads, bled the clutch, changed oil & filter and re-greased the headstock bearings. I'm running out of stuff to do now so I'll have to ride it now.