Lean surge @ 3100-4200 RPM
03-04-2012, 04:59 PM
#1
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Lean surge @ 3100-4200 RPM
I recently took my bike to get dyno tuned at the local shop and they ran it a few times. After getting the bike back I was told that they had upped my HP and Torque numbers quite a bit, which they did but I still have a lean surge at my cruising RPM. The bike pulls flawlessly from any RPM, but on decel it backfires. The tech at the shop says he recomends a jet kit so the needles can be shimmed and maybe lighter diaphram springs. I am lost on this part as I dont know about needle shimming and profile recomendations, Especially for the pipes that I have, if that makes a difference at all. I have removed my PAIR and CARB components prior to taking it to the shop. Any help would be awesome.
03-04-2012, 06:50 PM
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Simply going to the hardware store or Radio Shack (if they still sell them) to get some small washers will go a long way. Many have had success just by shimming the stock needles 0.060". That's usually 2 washers per needle. They go under the needle so the needle is raised, thus allowing more fuel to flow, and correcting the lean problem on mid throttle.
03-04-2012, 06:58 PM
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Fantastic! I really didnt want to buy a jet kit just for needles. Thanks for the advise. Doing that tomorrow. On a second question, If I went to high mounts would that cause my jetting to be messed up with the extra 2' of tubing or since there is no restriction till it hits the canister there will be no change using my current cans?
03-04-2012, 08:37 PM
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Probably be no change. There is a restriction in the stock header coming off the right side. Some guys remove it, some don't. Some swear it's engineered in. I don't believe it, but then I'm a skeptic...
Oh, if you have a digital calipers or micrometer, bring that to the store with you to measure the thickness of the washers. I looked a little silly measuring them at Ace but I didn't care. That was almost 14 years ago and although people still look at me funny, I don't think it was because I was measuring washers to the .001".
Oh, if you have a digital calipers or micrometer, bring that to the store with you to measure the thickness of the washers. I looked a little silly measuring them at Ace but I didn't care. That was almost 14 years ago and although people still look at me funny, I don't think it was because I was measuring washers to the .001".
03-04-2012, 10:06 PM
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I was planning on taking a digital mic to ACE tomorrow. I did see the restriction when I put my dan motos on and yet I know Honda does everything for a reason... but that just looks like they "Forgot" to cut the excess pipe on either side of the cross-over. I dont like it because it causes one of the pipes to look like its running richer than the other. Did you end up cutting them out or just "plug and play"?
03-05-2012, 01:57 PM
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Nice! I shall do the same. I pulled the rear slide and the shim stack was at .061 and then noticed that the cap for my front carb sync was missing. I bought a new vac cap and on my way to work I will try it out so see if that may have been causing my lean condition. If not then I will pull the carbs out check the front. It looks easier to pull than try and remove the slide when the carbs are installed. Now, if they are both at .060 should I shim more? If so what increments?
03-05-2012, 04:50 PM
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Funny Looks
Probably be no change. There is a restriction in the stock header coming off the right side. Some guys remove it, some don't. Some swear it's engineered in. I don't believe it, but then I'm a skeptic...
Oh, if you have a digital calipers or micrometer, bring that to the store with you to measure the thickness of the washers. I looked a little silly measuring them at Ace but I didn't care. That was almost 14 years ago and although people still look at me funny, I don't think it was because I was measuring washers to the .001".
Oh, if you have a digital calipers or micrometer, bring that to the store with you to measure the thickness of the washers. I looked a little silly measuring them at Ace but I didn't care. That was almost 14 years ago and although people still look at me funny, I don't think it was because I was measuring washers to the .001".
Ok, I'll risk my good reputation and step into this asking "why might they still look at you funny"? Perhaps they thought for this type of performance
.001 was not precise enough? Maybe it was the micrometer you were holding and they'd never seen one before? Maybe they were all democrats and saw your sceptisism as a challenge to there comfort zone.
Last edited by zxbud; 03-05-2012 at 04:53 PM.
03-05-2012, 07:10 PM
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Greg and I have never met but I can promise you he is one of the most exacting people I know. We have done deals - more than one - he is the consumate critic of engineering shortfalls. He has his version of the work-around and for me, his solutions for the Superhawk suspension were great.
03-05-2012, 11:55 PM
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Greg and I have never met but I can promise you he is one of the most exacting people I know. We have done deals - more than one - he is the consumate critic of engineering shortfalls. He has his version of the work-around and for me, his solutions for the Superhawk suspension were great.
03-06-2012, 05:23 PM
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Thanks for the props, Doug! 
Zxbud, I take no offense to your comments, and figure you're just razzing.
Squid, I highly recommend you just cap that nipple and see how she runs. Normally, on stock non-CA bikes that nipple is not there and is replaced by a small allen screw with a sealing washer. Since you're on the west coast it's best to assume you have a CA bike and that all the CA emissions crap has been removed. That nipple most definitely should be capped and WILL cause some rideability issues. It's basically the same as having a vacuum leak.
Zxbud, I take no offense to your comments, and figure you're just razzing.Squid, I highly recommend you just cap that nipple and see how she runs. Normally, on stock non-CA bikes that nipple is not there and is replaced by a small allen screw with a sealing washer. Since you're on the west coast it's best to assume you have a CA bike and that all the CA emissions crap has been removed. That nipple most definitely should be capped and WILL cause some rideability issues. It's basically the same as having a vacuum leak.
03-06-2012, 06:01 PM
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Alright I got back from a ride after plugging the line and letting the snow melted off the roads and still is lean and both needles shimmed at .060. So am I looking at a new needle profile or shim it up another .020 on Fr / Rr?
03-08-2012, 07:30 PM
#13
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Interesting, subscribed to learn more. I have a horrible lean spot at cruise around 3k. Havent opened the carbs yet to see if PO did anything to them, but I will this week in between trips to Daytona for bike week. Good info here!!
03-09-2012, 05:26 PM
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Yeah, I'd go another 20 thou. This is verified lean by using the choke, yes?
Any more and I'd start looking at bumping the mains a few sizes, if you haven't already done that. The DanMoto's are pretty free-flowing from what I understand.
Any more and I'd start looking at bumping the mains a few sizes, if you haven't already done that. The DanMoto's are pretty free-flowing from what I understand.
03-09-2012, 06:19 PM
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Greg you just mentioned something, the choke. Mine runs good with the choke half on in that same rpm range and the OP. But turn off the choke and cruise at 3k or so and it bucks and kicks. Sound the same as the issue that the OP is having?
03-09-2012, 08:00 PM
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^ yes, that's exactly it. By pulling the choke half out, you are enriching the fuel circuit. It's a good check for estimating rich/lean conditions. On the contrary, if it runs worse with the choke out, you may be running rich.
03-11-2012, 11:38 AM
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Sorry for not checking up on this as I should be. Got a new project taking time up. Thanks for all the input and 00SUPERHAWK we do have the same issue. I dont care about thread "Jacking", all the info in one place is good. I havnt messed with my bike yet, rain for 2 sollid weeks is slowing down that progress as it is out side and I have no garage to work in. I will have to have it done by the 2nd of April so i will keep you all updated as to what I find out over the next week or so.
03-11-2012, 12:02 PM
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Cool thanks Squid. Made my adjustments but havent put it all back together, waiting on one of the higher ups to chime in and give me some info. And same here its been raining for some time so Im in no rush to get out on the road.
03-11-2012, 06:28 PM
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I know what its like to wait for answers but some times we just gotta try things by the trial and error method. I have had my carbs off about 5 times now trying to get the set up to my liking. Basically there is not a cure all fix for me becasue I am the only person I think who actually has the model of Dan Moto pipes on this bike. I am just for a ball park instructions as far as needle shimming and when I should go up to a bigger main jet. Now that I have that info I just got to make time and get a warm dry garage to try it out in.
03-13-2012, 06:36 AM
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Well adjusted mine and it went the other way, To Rich! So now Im either gonna return the needles back to there original setting with that included shims. Or I might adjust the Rear Carb and not the Front as I have read some folks have done.
UGH, I knew there was a reason I was thinking of buying a bike with FI..........
UGH, I knew there was a reason I was thinking of buying a bike with FI..........
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