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Discussion Starter · #21 ·
Thanks Vinish. So I’m thinking I’ll start with 210 main jet, and the 58 pilot. Any suggestions on initial setting for the needle?
 

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If I recall correctly, the FP needle has five clip positions. I recommend starting with the clip in the 4th slot from the needle tip (2nd slot from the blunt end).
 

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Discussion Starter · #23 ·
Interesting day with the VTX. I have to say before I started this it felt very anemic. Poor overall power and throttle response and backfiring everywhere.

So today I started by installing the 210 main jet and the 58 pilot. Felt like I had some improved mid range, but Bike stopped pulling well before topped out. Also, Low end would hesitate majorly when I open the throttle and then sort of catch up to itself. Also experiencing popping on decel.

figured I’d try to fix the top end first, so I went up to the 215 main jet. This did improve power greatly on top. Mid range seem even more improved as well. Still have the problem on the bottom and major off-throttle popping like crazy. Back to the garage.

I installed the number 60 pilot jet thinking that perhaps this would cure the popping and maybe my low end. This did make a huge improvement in low in throttle response. So the bike is running pretty darn good now. Still occasionally have a slight hesitation of the bottom and a fair amount of popping. I figure I will mess with the needle jet tomorrow, it may be air fuel the next day.

With the bike in its current state I finally feel like it has some power. I’m definitely not done fiddling with it, but I am Super happy to be making progress.

As always any input is appreciated. Cheers all.
 

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Great results so far but I have a concern. There is a specific process to go through to properly rejet/tune the bike and I fear you are not following this process. As an example, you make no mention of needle clip position in your description above. The process is clearly outlined in the "carb what affects what" sticky thread.
 

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Discussion Starter · #25 ·
Yes, your concern is valid.
I did read the “what affects what” thread. Though I haven’t followed the procedure exactly, I did find it very informative. Admittedly I have taken shortcuts by changing multiple jets and not going in order. My objective here was to reduce the number of times I had to have the bike apart. I’m not sure if it will work out that way. Never the less I feel I’m closing in on it. 🙂

Needle has 5 positions and I’m in the middle. I think the main jetting is good where it is, as top end performance is strong. Mid-range throttle response is also good. My only remaining issues are popping on deceleration, and a slight bog off the very bottom. Do you think these are issues that would best be addressed by fiddling with the needle? Or should I be thinking about the pilot jet and or A/F screw?

thanks for staying engaged. I do appreciate the input.
 

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My guess would be the A/F screw but it could also be the needle. The reason to do the tuning/rejeting in the specific order listed is that it allows you to optimize the "parts"/carb circuits in such a manner that you should not need to go back and readjust a part/circuit you have already optimized. Your approach leaves you in the specific quandary you mention - that is, not knowing which part/circuit to adjust.
 

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Discussion Starter · #27 ·
I see. I am starting to understand the value of the process. After spending a second day swapping things out I am feeling a bit defeated. I thought I had the main jet sorted. Now I don’t think I do. Bike is stumbling / bogging when I open the throttle at 3500 rpm. I don’t know whether to go up or down with main jet. Currently I have a 220 main in the bike. I’m ready to do the procedure step by step, but I don’t know if I’m too rich or too lean with the main jet.
 

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I see. I am starting to understand the value of the process. After spending a second day swapping things out I am feeling a bit defeated. I thought I had the main jet sorted. Now I don’t think I do. Bike is stumbling / bogging when I open the throttle at 3500 rpm. I don’t know whether to go up or down with main jet. Currently I have a 220 main in the bike. I’m ready to do the procedure step by step, but I don’t know if I’m too rich or too lean with the main jet.
Did you try my setting from page 1 on my dyno graph?
 

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With the currently installed jets, follow the process and the results from the test described as the first step will tell you if you are too big or too large. This, I believe, is the 2nd gear from 25 to redline/fuel cutoff test. Don't get arrested or a speeding ticket while doing these tests :)
 
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Discussion Starter · #30 ·
JPT I did try your settings. With the #60 and the 210, the bottom end response was better. However Nothing seems to be working for the top end. I can’t get a strong pull to 4500 rpm. I mean this bike should do an indicated 90mph pretty easy right?
 

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JPT I did try your settings. With the #60 and the 210, the bottom end response was better. However Nothing seems to be working for the top end. I can’t get a strong pull to 4500 rpm. I mean this bike should do an indicated 90mph pretty easy right?
Yes. My 5th gear feels like a 3rd gear. I have full power in every rpm range. With my batwing off, I can easily pull to 110 mph.

What is your elevation? Did you try tweaking the AF screw with the 210/60/5.5 jet/needle setting? I'm at about 100 ft here in Long Island NY.
 

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Discussion Starter · #32 ·
I’m at 5280 in Denver, so that’s one issue. I’m waiting on Glen’s A/F screw so I haven’t messed with that yet. Also, I haven’t changed the clip position from 3. So there are a couple things to mess with. You have yours 5.5 from the blunt end? I think my needle only has five grooves in total.
 

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I’m at 5280 in Denver, so that’s one issue. I’m waiting on Glen’s A/F screw so I haven’t messed with that yet. Also, I haven’t changed the clip position from 3. So there ar
Yeah, my tune is probably dumping too much fuel for your elevation... I'm not a tuning pro, which is why I took it to a dyno tuner that builds race carb'ed bikes.

I would assume that putting things to my exact tune, then playing with the A/F screw (when you get it), might give you a good tune. But as I said, I'm not a pro, and attempted following the guide provided here. When I did, it put me far off of my dyno tune. The guide would never have put me to 5+ needle position.
 

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You achieve a half step in the needle (e.g. 4.5) by putting a tiny washer under the needle clip. As for your high rpm problem, check out the rest of the carb. Look and remove any dirt or varnish. Check out all rubber parts for dry rot or cracks. Look VERY carefully at the rubber membrane on the main slide (the slide that holds the needle). Make sure your jets are clear. Keep at it. You will figure it out.
 
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Whatever is the red line for the bike is where the fuel cut off will occur. I do not believe the bike actually stops the fuel flow as there is no way to do that. The fuel flow and carb are all mechanical operations not electric ones and there are not feedback loops to these mechanical operations that would allow fuel shutoff. My guess is that the plugs stop firing at the rpm limit and at the max speed limit. However, I am not sure about this. Someone with more knowledge than I have, please chime in. How does the bike "enforce" the rpm and max speed limits?
 

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Whatever is the red line for the bike is where the fuel cut off will occur. I do not believe the bike actually stops the fuel flow as there is no way to do that. The fuel flow and carb are all mechanical operations not electric ones and there are not feedback loops to these mechanical operations that would allow fuel shutoff. My guess is that the plugs stop firing at the rpm limit and at the max speed limit. However, I am not sure about this. Someone with more knowledge than I have, please chime in. How does the bike "enforce" the rpm and max speed limits?
I agree with this! There would be no other way to cut, other than cutting spark. With the loss of spark, I guess it would cut vacuum, thus also cutting fuel delivery to the carb.

I see different rev limits on different posts. One says 5,600.
 

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Discussion Starter · #38 ·
Whatever is the red line for the bike is where the fuel cut off will occur. I do not believe the bike actually stops the fuel flow as there is no way to do that. The fuel flow and carb are all mechanical operations not electric ones and there are not feedback loops to these mechanical operations that would allow fuel shutoff. My guess is that the plugs stop firing at the rpm limit and at the max speed limit. However, I am not sure about this. Someone with more knowledge than I have, please chime in. How does the bike "enforce" the rpm and max speed limits?
Right, I realized that the bike doesn’t have a fuel pump after I posted my initial rev-limit query. I’m wondering if the power loss is just me hitting the Revlimiter and I am simply expecting too much. On the other hand I feel like the bike should be able to pull at least 90 mph without a problem. The input and encouragement has been great guys. I’m gonna keep at it. This bike is a lot of fun to ride even with these issues.
 

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Discussion Starter · #39 ·
Yeah, my tune is probably dumping too much fuel for your elevation... I'm not a tuning pro, which is why I took it to a dyno tuner that builds race carb'ed bikes.

I would assume that putting things to my exact tune, then playing with the A/F screw (when you get it), might give you a good tune. But as I said, I'm not a pro, and attempted following the guide provided here. When I did, it put me far off of my dyno tune. The guide would never have put me to 5+ needle position.
Yeah, if I can’t get it sorted i’m just gonna take it to a tuner. I’m probably going to try Vinish’s Advice first and make sure there’s not a bigger issue like vacuum loss or dirty carb first. Good to know I’m not the only one that struggled with the procedure posted here. Though I do think it is a good procedure and good information.
 

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Yeah, if I can’t get it sorted i’m just gonna take it to a tuner. I’m probably going to try Vinish’s Advice first and make sure there’s not a bigger issue like vacuum loss or dirty carb first./b] Good to know I’m not the only one that struggled with the procedure posted here. Though I do think it is a good procedure and good information.
That is good advise and a good plan. If you are losing power in the higher RPMs, my guess would be the same, vacuum lines and/or carb diaphragm leaks.

The carb guide is a good procedure. I would have come to a good working tune, BUT, it would not have gotten me to the tune I currently have. Even Factory Pro's guide would not have gotten me to this current tune. Several members of this forum, the sister forum and many facebook groups have found that even after using the guide to get to their tunes, they tried the tune I have and it resulted in decent power gains.

My builder was in long conversations with the Factory Pro's team during the tuning process. I really trust my builder, he did my work on my last bike (zx12r ninja), and is known in this area. He was able to gain a very good understanding of how the Factory Pro needle works. His theory is that the needle height is the most important thing about the tune. With Factory Pro, the jets are just for idle and very high rpms, every other part of the RPM curve is needle height.
 
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