Thanks for the advice. Carbs were in a very bad state when I got them. I have replaced most parts as they were in a bad state. I even changed the floats just make sure. I will take on board all your advice and as soon as I am able to work on the bike again I will post an update.
XV 750 Cafe Float Levels
- Thread starter Sorcli
- Start date
Ok everyone, had another go yesterday. Had put the original idle jets back in and gave it a go. The bike started but would not idle. it ran as long as I revved it. As soon as it was warm I had to close the enricher off and it ran slightly better but still would not idle. At least now it will start. Tried turning the idle screw out a half turn, still would not idle, then another half, still would not idle. At this point I thought I would check the carbs one last time. Took them off and blocking off the various channels, I ran liquid through all the pilot ways, I am now 100% sure that every single way is totally clear. One thing I did notice is that the idle screw will easily screw down and the point comes out int the carb intake, is this normal or has the previous owner screwed it down too much?? One thing to add, I got popping from the exhaust when accelerating which I presume is due to the main jet still not being big enough? Any advice would be appreciated.
DohcBikes
Fuck You.
We are tuning for short pipes on a metric v-twin.
Do this.
Move up 1 size on your pilot and 3 sizes on the main
2 turns out on the mix screw.
yes it is normal for the screw tip to portrude through the floor of the carb when at soft seat. it might be around level with the floor of the carb when 2 turns out. Or it might not. You tell us.
Do this.
Move up 1 size on your pilot and 3 sizes on the main
2 turns out on the mix screw.
yes it is normal for the screw tip to portrude through the floor of the carb when at soft seat. it might be around level with the floor of the carb when 2 turns out. Or it might not. You tell us.
Thanks. I had a 45 pilot in and it was virtually impossible to start when it did it wouldn't run well at all and gave all the signs of flooding. Now with the stock pilot jets at least it starts. I have a 125 main jet but have 130s at hand if necessary. But would like to get it idling first to sync before looking at changing the main jets again.
Been messing with the bike all morning. It starts, but hell is it difficult to get it to start. No enricher needed at all. If I wasn't using jump cables off my car battery it would be impossible. When it did start I had so much difficulty getting it to idle. But when I rev it it sounds sweet. I did get the opportunity to check if it had any vacuum leaks and it doesn't. I know it's just a matter of getting the setup of the pilot screws and the sync between the two right now. But I just gave up for today after trying so long to start it and all it does is fire a few times while trying to start. Just want to say that anyone who knows how to get these carbs right is a genius! 
DohcBikes
Fuck You.
Thanks anyway? He's pointing to an issue, regardless of your plan it is not advisable to make carb changes if your ignition system is not running at peak performance.Sorcli said:
p.s. its not the carbs that make it hard to tune the idle it's the low vacuum signal, which you made worse with short pipes
I didn't mean to offend. I just meant I have a nice new battery waiting, my temp has run low so I jumped it. My primary problem is getting it to start and keeping it running. I'm not really tuning the carbs as much as trying to get it to run. So thank you for any advice, as the problem does not seem to be constantly the same I'm greatly confused. I'll just keep methodically going through it and I'm sure I'll get improvement in the end.
DohcBikes
Fuck You.
I'm not offended. Yes you need to continue trying things, and that includes suggestions here. Try the new battery, what is the reason for waiting?
I've mentioned several times, the pipes are not helping. However I think you need to buy several sizes of jets and start tuning the thing correctly. It's a custom build with how much into it, and you know how many people are hesitant to just buck up and buy some jets to make it run right? Jetting threads can get very frustrating if the tuning is restricted to a couple sets of jets, and the person wants to wish the carbs into tune.
I've mentioned several times, the pipes are not helping. However I think you need to buy several sizes of jets and start tuning the thing correctly. It's a custom build with how much into it, and you know how many people are hesitant to just buck up and buy some jets to make it run right? Jetting threads can get very frustrating if the tuning is restricted to a couple sets of jets, and the person wants to wish the carbs into tune.
I've tried some larger pilot jets but it kept flooding, I'm getting better results with the stock size. I've got slightly bigger main jets and others even bigger ready if needed. The strange thing is that it's so difficult to start, but yesterday when it did and I was using the thottle it sounded so sweet, but would not idle at all. Today, it's slightly easier to start, as I adjusted the pilot mix screw slightly but it doesn't run as sweet, getting a lot of popping from the exhaust and it still doesn't want to idle. I'm starting to suspect that I may have a compression problem on the from cylinder, perhaps the guy who rebuilt the engine didn't do a good job. So I want to do a compression test next.
I was just following other advice and one guy who has the same setup as me who is running stock 41 pilot jets, and stock mains with a decent result (he can ride it but gets popping when the throttles' open (too smaller main?) So I left my 125 mains as it just seemed logical and it seems to run (often) ok when using the throttle. My main issue seems to be start/idle. This evening it didn't want any enricher, when I managed to start it and when it does run if I play with just the left carb min/butterfly I'm able to keep it running it I try to use the right side screw it doesn't have a good result, which I find really strange. Seems as if the two sides want quite different adjustments which is very strange as I bench synced the carbs and they open in unison. Any ideas?
coyote13
Over 1,000 Posts
And again, the problem with your idle could be that your battery is shot. Had a battery on its way out a few years back, bike was hard to start and very difficult to keep running at idle, the headlight would get brighter whenever I blipped the throttle. Replaced battery, ran like a champ. Try it, you'll like it.
I popped my vacuum tester sync tool made out of two beer bottles on tonight and just tuned it over to find the left carb has a lot more vacuum than the right even with both butterflies totally at the minimum rest point/totally closed. That's what started to make me that perhaps I have for compression on the front cylinder possibly Value adjustment?
