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Question for 1700 owners

5K views 21 replies 13 participants last post by  R_W_B 
#1 ·
Hey everyone, my dad has a 1700 Vaquero with about 1350 miles on it. One thing I've noticed is that at idle, cold or hot, doesn't matter if you give the throttle a good bip and raise the RPM's up to about 2500, and I'm not talking about raising the RPM's gradually at idle to 2500rpm, just a quick blip of the throttle, there will be a clunk, and it's fairly loud. The bike runs fine, with no issues, but I'm just really curious to know if this is a normal noise for the 1700 engine or if it needs to be checked out?
 
#2 ·
There should be no clunking sounds just a smooth bark from the exhaust.There may be a loose engine bolt somewhere. I would have them check the upper mount first. My VAQ makes no such noise.
 
#3 ·
Are you talking about a back-fire? A loud cluck sound doesn't sound right to me, but a back-fire, absolutely...which is usually caused by unspent fuel sparking in the exhaust.
 
#4 ·
No it should not be doing that.
 
#6 ·
It's not a backfire, it's an audible clunk when you blip the throttle fairly hard. Maybe I need to take a video so everyone can hear it.
 
#8 ·
never heard no throttle clunk in mine.
 
#10 ·
Really ? I think you mean rum and coke, don't ya ?
 
#12 ·
Yep i have the same noise on my Nomad.
Sounds to me like a bearing knock in the bottom end, bike seems to run ok its got 12000k's on it now. I have my suspicions that it may be fuel knock when you blip the throttle really quickly. Due to the built in delay these bikes seem to have. I gave mine the "throttle mod" treatment and seems to have reduced the incidence.
My bike has done it since new, but as i said it seems to run ok.
 
#14 ·
Don't know what kind of Knock you are talking about.

When you blip the throttle, does the engine stutter and hesitate ?

If so is this when you hear the clunk or knock ?

If you answer yes to both the above then, yes I have the same thing on my 2011 Nomad. It got worse when I put the throttle mod on it, prior to the throttle mod it mostly did nothing when I blipped the throttle, no rpm gain, just kinda nothing. The throttle lag is the result of Kawa's electronic throttle.

I have to gradually increase rpms before I blip the throttle or else I get a very detectable knock. Evidently the ECM is not able to deal with a fast increase of throttle from idle (resulting from the throttle mod).
 
#21 ·
No stutter or hesitation, just a clunk noise when you blip the throttle. If you gradually raise the RPM's it doesn't happen, like you stated.
My 2010 Nomad does the same thing. Bear in mind those are large pistons slinging around. Because of the single pin crank design of this v-twin, if you goose the throttle from idle, you will get a "slap" from the engine. I don't think it is anything to worry about.
My 2000 has even bigger pistons sloshing around in it and there is no clunk or knock on a good blip of the throttle at idle.
 
#16 ·
My 2010 Nomad does the same thing. Bear in mind those are large pistons slinging around. Because of the single pin crank design of this v-twin, if you goose the throttle from idle, you will get a "slap" from the engine. I don't think it is anything to worry about.
I'm not so sure on that Timberwolf (with all due respect). My previous Harley had a single pin crank (all Vtwins do) and I never got anything like that. I think it's the ECM timing and reactions to the throttle.

I try not to blip my Nomad since I'm afraid it's a pre-ingition knock. In normal engine (that's not worn out) there should be no piston slap or rod beaing knock.
 
#19 ·
I've been concentrating on riding for while and my work schedule has been crunched. Soon I plan to install my new PCV w/Ignition. I don't have anything on the bike but Cobra Tri-Ovals, so I can't put in David's full blown (big air) map. But I'm gonna see if the Power Commander slip on map download takes care of this situation.
 
#22 ·
Thought I'd update this thread. I put a PCV (w/ignition) on the bike some time ago, but for the first few map experiments I had only limited success in eliminating the stutter and knock. However over time with much experimentation I now have a map that eliminates most of the blip stutter (and knock) in all but the most brutal very fast blip. In fact I'm very pleased with the overall performance and low end response of this map. (running stock air and cobra tri-oval slip ons).

I would be glad to send the map to anyone that wants it, but again these bikes are all a bit different as we can tell by the above replies. I firmly believe that this blip issue is an ECM problem. With the ECM problems of the 2010 time window I think Kawa has simply blown the quality control of flashing some of the ECMS going into these model bikes. In other words I don't think every same model's ECM has the exact same flash. I have no proof of this but I can't figure why most bikes don't do this but some do.

I previously pulled my entire intake system off down to the jug intake ports. I put new O-rings and hylomar universal blue sealant on the manifold to jug area, and on the Thunder Mfg gasket on the throttle body area. I meticulously reassembled everything with no issues. I do not have any vacuum leaks. I think it's a defective factory flash on the ECM, just my theory on it.
 
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