Honda XRV Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
35 Posts
Discussion Starter · #1 ·
I have done the “standard” modification to my Vigor by taking out the end baffles, fitting a 175 main jet and removing the airbox snorkel. All seems well at idle and at speeds over about 35 mph but I’m having problems at slow speeds between (very roughly) about 15mph and 35mph (somewhere around 3000rpm). It feels like fuel starvation – there is a slight “tugging” like the brakes are being lightly tapped on and off. Applying a bit of choke helps this a lot so it seems like the issue is a very lean mixture but only at low speed - possibly an issue with the slow jet. I’ve done several engine chops after a high speed run (i.e. main jet speeds) and they give the right spark plug colour. I have progressively unwound the mixture screw – which seemed to be helping the low speed issue – until the mixture screw came out altogether and is now lost on the road(!). Que Ebay. I’m thinking that the problem might be that, although the increased main jet is coping well, the slow jet is just not big enough to feed the engine with enough fuel with the increased air flow and needs to be replaced with a bigger one. I haven’t seen any mention of upgrading the slow jet in any of the relevant threads on Vigor modifications. Has anyone else had this issue?
 

·
Registered
Joined
·
699 Posts
It's most likely that your slide lifter is stuck open.
There is a fork that lifts the throttle slide when the throttle is first opened, it's connected to the throttle butterfly cam.
They stick in the up position and bugger up the low throttle response.
Also check that your static air reference pipe is properly connected and routed. The hose comes from a boss on the left side of the carb, then to a splitter and into two more hoses. One dangles down behind the engine, the other sits up under the seat.
You should not have removed the airbox snorkel. You should not make any changes whatsoever to your airbox or filter arrangements.
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #3 ·
Thanks for that very quick and helpful response. While I wait for the new mixture screw to arrive, I've replaced the snorkel and had a look at the static air reference pipe and the throttle slide lifter. The static air reference pipe all looks OK. I assume the slide lifter is the thing in the middle of the close-up below? It all seems to be working OK (and the carb has just had a professional ultrasound clean so it should all be OK). Do you think the problem could have been caused by having no snorkel?


Automotive fuel system Automotive tire Motor vehicle Automotive exhaust Gas Automotive fuel system Automotive tire Motor vehicle Gas Auto part
 

·
Registered
Joined
·
699 Posts
OK, as long as that little spring loaded lever is rotating in line with the cam lifter on the throttle pully then it should be working.
The snorkel could have caused the stutter - these CV carbs are extremely sensitive to intake turbulence.
When you put your mixture screw back in make sure you have the packing washer, spring and O ring in there too.
There is something else you can look at - if you look into the carb throat just behind the butterfly you will see 4 tiny holes, these are the pilot fuel circuit bypass and they can become clogged. They are absolutely microscopic - you may not even notice them unless you know where to look. To clean them it's either a strip and in the ultrasonic bath or you may be able to clear them by spraying carb cleaner up into the mixture screw hole - don't be tempted to poke wire down into them.
 

·
Registered
Joined
·
35 Posts
Discussion Starter · #5 ·
Sorted. Turned out it was taking the snorkel out that upset it. I've put it back in, re-set the pilot screw and she's back to her old self. And thanks, Bobn, for reminding me about the packing washer: the (used) pilot screw arrived from Ebay without one(!) - and I wouldn't have realised. Another delay caused by getting the washer but all's well that ends well.
 

·
Registered
Joined
·
699 Posts
Happy to help!
 
1 - 6 of 6 Posts
Top