Surging

[cyclecat]

2006 - 1600 Nomad belongs to our friend Charlie and we don't know enough about the 1600 to really know whats going on so we need some advice. The Nomad is stock and is not a California model. 4 rides ago, Charlie told me his Nomad had started to surge a bit in first gear, at slow speed. He also mentioned that the exhaust sound seemed a bit different to him. He brought the Nomad over to us and Brian took her for a ride. He noticed the surging a bit but couldn't tell if the exhaust sounded different because he does not ride that Nomad so she sounded normal to him.

3 more rides and Charlie says the surging has gotten worse. He went to start out yesterday and as he letting out the clutch and slowing giving her gas, she surged forward and he had to pull in the clutch and touch the brake to slow down. Charlie went through a construction zone yesterday and in 3rd gear he said his Nomad is doing the surging thing.

What we do know is when the throttle is turned and let go, the throttle immediately pops back to the off position but the engine takes a good 20 to 25 seconds to idle down. We have tried adjusting the idle screw and it makes no difference. When I do the same thing to Ruby, turn the throttle and let go, Ruby instantly idles down. Charlie's Nomad was not doing this when he got her last fall and the first couple of rides this spring but the problem is getting worse. He'd rather try and fix the problem than take her to a dealer since he has to take her to the States because that's where his warranty is good.

[cactusjack]

First thing I would do is give the throttle body and butterfly plates a good cleaning.

[cyclecat]

He has cleaned the throttle bodies and the butterflies are working okay.

[Cajunrider]

Originally Posted by cactusjack

First thing I would do is give the throttle body and butterfly plates a good cleaning.

That thought was the first thing that came to mind. If the throttle instantly pops all the way back to normal, it doesn't seem like the throttle linkage would be hanging up.

[macmac]

I think you will find a vacuum leak. This is un-metered air getting around the throttle plates.

In the throttle plate body is a few vac lines. One goes to the vac pod that runs the reed valves.

You need long needle nose pliers to get at it, and the gas tank needs to be off. I would first pull the tank, then pluck off the tubing after finding the vac pod I refer to as Medusa's Head.

Check the vac line where it fits on the brass throttle body for being loose, cracked brittle, or just plain blown off. Have one of the men draw by mouth on the tubing, to see if the vac pod holds their tougne to the bitter end. If it does not the vac pod tubing end or the vac pod are bad.

The throttle body either has other tubings or caps, made of a rubber or plastic like material, and any of those could be bad as well. Any items down line may be bad on any other vac tubings.

Another way to check, is to use a old fashion brass plumbers torch on a common propane bottle NOT LIT. With the engine running you turn on the torch and aum it at items where there could be a vac leak. If the rpm changes any you are upon a leak.

I used to use WD-40 for the same thing, but the last can i bought with a built in wand refused to act as extra fuel. I don't know if that type can has a different formula and the older type cans have the same old forumla or not.

About the only other places a vac leak can happen on a Vulcan are the throttle plate shaft ends, or the O rings on the intake manifold.

If this problem gets worse it will be in the 'Hunting' catagory of vac leaks. Hunting iis when excess air by-passes the throttle plates in any way, that raises the RPM to a pretty high rpm, then as the fuel mix becomes overly lean the engine will starve for fuel and the rpm will drop like a rock. This will produce a near stall, but usually the mix becomes rich enough and the whole cycle starts over.

The only real difficult part is getting to the hose ends since even with the tank off they are buried a bit deep.

[ringadingh]

If the throttle body cleaning and checking for a leaking vaccum hose don't fox it check the throttle position sensor, it may need calibrating or replacement.

[skimo]

Originally Posted by Ringadingh

If the throttle body cleaning and checking for a leaking vaccum hose don't fox it check the throttle position sensor, it may need calibrating or replacement.

+1 read this for more info

http://www.gadgetjq.com/tps_adjust.htm

[cyclecat]

We're pretty sure it's a vacuum leak also but just in case there was something different on the 1600 than the 1500, I thought I would ask you guys with the 1600's.

[macmac]

The tubing to the vac pod should be the very same as a 1500. The seats bolt on different. I can't recall of there is any difference in the nacell, or wiring under it.

The rain drain thru the right ft of the tank is the same as is all other drin lines on right rear.

The fuel pump is slightly different, but the pinch fitting is similar to get the fuel line off.

I am 99% sure you will find a bad line end or a bad vac pod that feeds the reed valves, and if not a blown off cap.

The throttle body has a capped off brass port that would feed vac to the California carbon canister. Since this isn't a cali bike there is no tubing there, just a cap, which could be brittle from heat, cracked from the same, overly expanded for the same reason, or just plain blown off, but I doubt it is totally gone.

Usually with 'Hunting' leaks the part is still in place and functions in a limited way. Visably the bad part may look just fine too, but upon closer inspection will be found bad.

Pretty much on any engine all caps and tubing should be checked once a year for condition, and replaced every other year.

I tend to replace these every year, so I don't get caught off guard. I will allow a cap in very good shape still or a tubing line to remain, so long as it is sealing tight, usually hard to simply pull off.

Anytimes the tank is off I tend to check everything I can see, and everything i ever heard of being a problem. That means i check all water hose clamps, the wire harness where it turns down behind cly 2 for signs of chaffing. I look for white powdery residue which is coolant dried, and lube the throttle linkage after cleaning it first.

I check what wire terminals are there, to visually see they are snug looking and wiggle many to sort of clean up the terminals.

In this case I would be wanting to clean and snug the wires to the throttle position sensor, and make sure the part is bolted up snug too, and that o wires there show any sign of chaffing.

[skimo]

All the more reason to get some chuckster coasters and eliminate the potential problem all together.

[cyclecat]

We temporarily marbled the reeds but I haven't heard yet if it done any good. Couldn't find any other hoses that needed replaced, that are blown off or come apart but did a temporary marbling just to see. Charlie wants to leave his Nomad stock since he has warranty left, in the States, until 2012. The 1600 seemed to idle down faster sitting in the garage but I will have to wait to hear if Charlie got out for a ride yesterday and how the surging is.

Don't need to buy plates; Charlie has a milling machine and a lathe in his shop and between him and I we can pretty much machine anything. We machined our plates and they fit perfect. I machined the guage pods in my sig line, and our throttle body plates for the air kits on the mill and both are perfect.

[dogdoc]

How about a good cable lubing (both).

[cyclecat]

Not the cables, we checked. Marbling did nothing so Charlie is off to Montana to see what can be done by the dealer. Hopefully they can fix the problem - well we are talking about a dealer - so maybe yes, maybe no, but one thing is for sure, they will look until they find something since it is warranty and will get paid by Mama Kaw.

Thanks for the suggestions and I will let you know what happens.

[blowndodge]

I would have bet Mac's answer would be correct as this malady sounds just like an intake leak. However, it could be the air temp or air pressure sensor going bad. since the bike is at the dealer I won't belabor how to check those two sensors or their locations...

[macmac]

A marble won't work at all, since that system is turned on and off by engine vacuum. At idle and lower engine RPM there is engine vaccum working on the tubing and on the vac pod. The vacuum is what turns the pod on to allow air to flow to the reed valves, but on the other side of a diaphram.

A non cali bike will be capped off at the throttle body, as well as have the vac tubing going to the vac pod where the reed valve tubings are.

If the tubing is in good shape, the cap is also in good shape, the vac pod itself is tested and holds vacuum, then the thottle plate shaft seals, are suspect, the o rings on the intake manifold are suspect, and the injection body seals are suspect.

The injectors are seated in seals that must not leak air.