Fitz
Senior member
- Location
- Cheshire UK
Just a quickie, I swapped my 40 year old Dels for modern brand new Keihin CR carbs which are OK for BHRC BEARS racing when I built my bike a couple of years ago
There was teething problems from the get go but I finally started to get on with them, I still have sluggish pick-up from small openings but as a race bike this is not a major issue
I had a problem at Mallory (UK) in the early season when the bike would only pick up on one cylinder, after going through everything electronic and electrical, I finally stuck my fingers up the inlet tract to find only one slide was lifting, it turned out to be the link arm that had come off the slide, it had rotated in the body. Whipped the top off re-attached everything and problem resolved, since then I lockwired the link arms to the slides so they cant slip apart. Piss poor design if you ask me but I have made more mods to resolve the problem
I had an issue with one slide lifting earlier than the other, obviously this meant they were lifting at different heights all through the throttle opening. There did not appear to be any way to adjust them independently
Before I go to Cadwell for the season close in a couple of weeks, I was going through the bike doing my prep work as I always do and thought I would check the carbs again. The link arm and lockwire was fine but the slides uneven lifting was present but worse
I dismantled the link arms, slides etc. The link arm that originally slipped off is now buggered, the 5mm hole has elongated to the point that it is wafer thin and would wear through very soon. I have ordered two new link arms. After talking to the UK supplier, he suggested that there should be clips on the bar running through the link arms which makes sense, he is sending two of these as well
So if you are using or plan to use CR's they are excellent and perform well, documentation and set-up manuals are non existent, I have found exploded diagrams if you need them
In the absence of anything else, I set up the needle position and size based on the advance curve from my Sachse ignition curve No 4 and info from the web showing which jets do what at a particular slide position, it seems to work but I am sure it could be better if I spent time on the dyno with a box of needles and jets
I still find that if you pull the choke all the way off when the engine gets warmed up and the bike running on both cylinders, it has poor pick up, lift the choke just a tiny amount and it runs fine all day, mixture seems good looking at the plugs
I am very suspicious about the original carb build, the UK supplier sent them without needle jets so they pissed fuel all over the floor from new, I found a few other little niggles through the season so after Cadwell, they are coming apart for inspection
There was teething problems from the get go but I finally started to get on with them, I still have sluggish pick-up from small openings but as a race bike this is not a major issue
I had a problem at Mallory (UK) in the early season when the bike would only pick up on one cylinder, after going through everything electronic and electrical, I finally stuck my fingers up the inlet tract to find only one slide was lifting, it turned out to be the link arm that had come off the slide, it had rotated in the body. Whipped the top off re-attached everything and problem resolved, since then I lockwired the link arms to the slides so they cant slip apart. Piss poor design if you ask me but I have made more mods to resolve the problem
I had an issue with one slide lifting earlier than the other, obviously this meant they were lifting at different heights all through the throttle opening. There did not appear to be any way to adjust them independently
Before I go to Cadwell for the season close in a couple of weeks, I was going through the bike doing my prep work as I always do and thought I would check the carbs again. The link arm and lockwire was fine but the slides uneven lifting was present but worse
I dismantled the link arms, slides etc. The link arm that originally slipped off is now buggered, the 5mm hole has elongated to the point that it is wafer thin and would wear through very soon. I have ordered two new link arms. After talking to the UK supplier, he suggested that there should be clips on the bar running through the link arms which makes sense, he is sending two of these as well
So if you are using or plan to use CR's they are excellent and perform well, documentation and set-up manuals are non existent, I have found exploded diagrams if you need them
In the absence of anything else, I set up the needle position and size based on the advance curve from my Sachse ignition curve No 4 and info from the web showing which jets do what at a particular slide position, it seems to work but I am sure it could be better if I spent time on the dyno with a box of needles and jets
I still find that if you pull the choke all the way off when the engine gets warmed up and the bike running on both cylinders, it has poor pick up, lift the choke just a tiny amount and it runs fine all day, mixture seems good looking at the plugs
I am very suspicious about the original carb build, the UK supplier sent them without needle jets so they pissed fuel all over the floor from new, I found a few other little niggles through the season so after Cadwell, they are coming apart for inspection
