Idling problem/Hotcams stage 2

A time ago ,I did some extra motor work on my 650 R ('00):- HRC piston

- Knibblewhite valves (intake 1mm OS, exhaust standard)

- Hotcams stage 2

- cleaned /matched up the head,nothing radical.

The carb is a a Mikuni Tm40,no probs before,great power.Other mods before: air box mods(12 holes of 35mm), no back fire screen,No Toil filter,Mikuni TM40, Evo (Monnier) exhaust line,stock motor.Bike is in SM trim : 15x 42 gearing.

With the extra mods,the bike was run in with richer carb settings ; from 25 to 27.5 pilot,main from 157 to 165, the leaner needle (Bruce Specs) but 1 clip richer. The bike wouldn't run fine(bogs,sputters) with the richer settings. I dropped the needle and the main to a 157. The bike runs fine now but wound idle longer than 10/15 sec,sometimes dies on traffic lights etc. Sounds lean, I tried some airjet and pilot settings but nothing really helps.The bike starts/runs fine warm or cold.No bogs,sputtering .

I have a spare crank with a Falicon rod now so I can put a 680cc kit on it.I want to solve the idling problem first.

I put the OEM Honda cam back in again yesterday and the idling problem is gone, cold - still Little rough when hot but no stalling. Could the Hotcams be the problem or the head work?

I just cleaned the ports a little,matched the intake piece .. let the intake rough enough( I think).I smoothed/matched the area where the valve seats meet the head, both on intake and exhaust. The valves were done by a pro (4 angle job).

Anybody probs before with the stage 2 or with head work?

Anyone? :thumbsup:

Did you degree the cam?

Something is wrong if you need that much fuel to run the bike. Even in a 680cc bike with a cam like yours but, with more lift I only needed 140 main at sea level. (that is with a Y-4 needle jet, 1.2 air jet) I would check the float level also. Something is up with the cam or intake leak :thumbsup:

did you check the valve spring bind? Valve guide deck height? Clay test on valve time?

I don't have/get the specs from Hotcams to degree the cam.

When the motor still was stock,but with all the other mods ,the dyno showed it was fine with a 157 main.It had no backfire screen,a No Toil filter,12 holes of 35mm in the side panel,OS headers and a race can.I'm @ sea level,+- 15°C.

The plug showed a light gray tone after a wide open run trough the gears.

Normally ,a Hotcams should be a plug-in cam with no other mods ...I clay checked the valve clearance because of the OS intake valves. With the OEM cam it idles smooth now ,so no intake leak I think (I checked several times).

Maybe it's the head work I done but it was minimal. Barnum said not to touch anything on the ports when I emailed him about this

Really this sounds like you have the cam timing advanced. when you put the stock cam in you probably got closer to where it should be. Degree the cam and let us know whats up!

I have a 11:1 wiesco stock bore with the stage II hotcam. I am still running the stock carb, and I do not have any head work done. Mine will only idle, with no throttle imput, for about 15-25 seconds before it kind of hick ups and quits. I just assumed it was too "lumpy" of a cam?

Degree the cam and let us know whats up!

I would but I don't find/get the specs to do it.


Mine will only idle, with no throttle imput, for about 15-25 seconds before it kind of hick ups and quits.

Thats exactly the same thing that mine does. :thumbsup:

It also makes a loud metallic/mechanical noise trough the airbox with the stage 2 when idling/low revs, little or no noise with the stock cam.

My stage 2 idles good and goes good,the cam leads the crank by 3 or 4 degrees.

I would but I don't find/get the specs to do it.


You don't need the specs for the cam to degree it. You do need a degree wheel and a dial indicator. A setup like that link would work great right in the bike.


The specs for you cam should be close to:

------------------------Stock -------HRC CAM

Exhaust opens degrees 45 bbdc ------55 bbdc

Intake opens degrees 15 btdc ------ 20 btdc

Exhaust closes degrees 15 atdc ------ 20 atdc

Intake closes degrees 45 abdc -------55abdc

Intake duration degrees 240 --------255

Exhaust duration degrees 240 --------255

I think you have more lift and you bigger valve is hitting the piston (just a little) on it's sides of the valve. Or the cam timing is off or both. This isn't good but, I would remove the head and look and make sure up will have Peace of mind down the road.

Thx Bruce for the specs ( I also have the HRC manual ) but was the Hotcams stage 1 not close to the HRC cam and not the Stage 2 (more aggressive than HRC)??

I modified the valve pockets on the HRC piston to make room for the OS intake valves. Did the clay test also and had 1.5 a 2mm clearance between valves and piston. The bike is running fine with the stage 2,I have done +- 1500km with it since.It pulls 15X40 very well (top 190km/h on a digi with 17" wheels).

It seems that other people gave the same problem with this set-up - HC piston + Stage 2 - even without the bigger valves and some head work....

The cam timing is wright on his marks . :thumbsup:

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