Topic: installed webcam 41 grind.. motor seems to run hot?

[garretcb750]

OK fellas, here is my story, last night I decided to tear into the motor for my bike, I had a webcam 41 grind cam sitting around for awhile an decided to go ahead and install it. I tore the motor out of the bike, installed the cam and got the motor back in the bike in one evening. The cam seemed to be very SLIGHTLY retarded on its timing. So I was skeptical of how it would run. When everything was back together it fired right up, sounded great, but it was running really hot. My question is this because the cam needs to be degreed? or is it running lean? Webcam says this is a "bolt in" cam. It seems to run too well to be a valve timing issue but I could be wrong.

[Sam Green Racing]

The 41 is a bolt in cam and should be OK at stock cam timing.

Sam.

[MCRider]

You are adding more air into the cylinders with a bigger cam, more then likely you are running lean.

Yeah that'd be my guess. May need needle adjustment as well as main jet. Does it pop on decel?

[KB02]

I've got the 41a in my 850 bike. I did need to degree it. I would listen to the other, though, as it does sound like it running lean.

[kos]

Also, verify ignition timing.

KOS

[Big Jay]

[Hasenkopf]

degree it anyway...why ?  because there is too much play around the cam sprocket bolts..... you cam thank me later   

[scottly]

No, the cam should not make the motor run hot. Were you riding the bike when you observed this, or running it stationary with no air-flow over the cooling fins? If the latter, use a fan next time..

[KB02]

Webcam says this is a "bolt in" cam.

Yeah, bolt in with one of these:

(nice and subtle, Jay.  (and I agree... ))

I've got the 41a webcam in my bike and it does not run hot.  One other thing to add to the suggestion of degreeing the cam is to check your carbs. This cam will let in more gas/air than stock, so if you are running stock jetting, you may be running it lean as well.

[michrobi]

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[johnyvilla]

I too installed a 41a in my 836 and it was 2 teeth off from the standard setting. No over heating.

[rlvitt]

I just dropped a 41a grind into my K0. It's running rich as heck. I've got #35 idle jets in and 120 mains with the needle dropped all the way now. It is still running rich and I'm having a bad time synching in the carbs. Also my inductive timing light will not pick up the spark signal to re check the timing though I'm running a Dyna electronic ignition and Dyna 5 ohm coils. I don't know where to begin to check for the problem. The idle is rough at 1000rpms and seems to smooth out by 3500 rpms. Does any one have an idea where I should start first?  Thanks

[MRieck]

Any aftermarket cam should be timed using an adjustable cam sprocket

[PeWe]

Ran Ok with old cam and same carbs?
I have had rich on low rpms. Horrible rich to start with, "Tsunami carbs" when they squirted fuel due to wrong ignition advance, full advance direct.

Step 2 was floats in carbs.
Clear tube verified that, show the result of float adjustments, float valves OK or sticking floats.

[rlvitt]

MReick, The cam was installed with an adjustable cam sprocket at TDC. And the Dyna ignition was timed spot on with a timing light. Since then I've tried to check the timing again and can't get a reading from the timing light even with the Dyna coils installed. I know the light works after checking it's function on my truck. PeWe's idea about checking the float levels is also something I've been checking, along with leaner jetting. The whole thing is that I don't know now if I'm working with just one problem (the carbs) or two (carbs and ignition). I'm planning on installing new float valves just to make sure the bowls aren't over filling. But, so far I've checked them with a clear tube and they seem to be cutting the flow of at the 25 or 26 mm level.

I've installed new idle screws with the holes in them as that is one of the K0's original designs. They're turned out 1 full turn as were the old solid air screws. The main jets are 120's. I'm going to drop them to 110's and see if that leans the combustion out more. The needles are set on the top step already.

What I would like to know, also, is what characteristics the 41a grind has in smoothness at idle. Should I expect a rougher idle and how much rougher? I've only had experience with stock cams so I have a lot of questions about street cams......

[MCRider]

I have a 41 in a 888cc engine with VM29 mikunis and a ported head, luscious, by MRieck. I did use a degree wheel and slotted sprocket to say that I did, even though its a drop in cam.  The degree wheel set it more accurately than the regular marks would have. The 41 is wimpier than a 41a. Mine is perfectly civil, idles sub-1000, and builds revs nicely. Call it pleasant. I'd say the same for a 41a.

Though a stock head and carbs will not lend any help to the cam, so it may be rougher running in your case.

[rlvitt]

MC, I was doing a little work on it today. It idled down at about 1100 fairly nicely with the "old" style idle screws installed. Still rich though. I found the #1 and #4 carbs dumping gas though. I believe I'm going to have to explore the floats again. Could be that I've got some junk up in the float valve though I blew them out with compressed air. Looks like I'm going to have to pull the bottoms off and change to 110 main jets and replace the float valves and put in a set of #38 idle jets in place of the #35's in there now.

I managed to check the timing and it was spot on at 3000 rpm. The light doesn't want  to work until the rpm's are above 2500 for some reason.  It seems to run nicely in that range any how. I'm still trying to figure out why the light won't function until the rpm's are raised......

[MCRider]

Sounds like if you have a rough idle its due to the carbs.

When you say the light doesn't work, what do you mean?

2500rpm sounds suspiciously like a stuck spark advancer, but that shouldn't affect the light. Just thinking...

[rlvitt]

I agree that it's probably due to the carbs. They are the original carbs And I know they've never been opened since the early. So it's a sure thing that the cam change means they need to be refitted for proper carburation. It's probably going to be a matter of mixing and matching until I get the right sized jets in place. But what bugs me now is that the timing light does not function until the enging reaches about 2000/2500 rpms and then begins to flash. The timing marks are advanced to the proper marks when I check. I don't have reason to believe that they are stuck in the advanced position though. However I sure would like to confirm that by being able to check them at idle speed.

[PeWe]

tried
the timing light sensor pointing at the other way?
another spark plug cable?

[seanbarney41]

try hooking your timing light power leads to a battery that is not connected to the bike...I read this somewhere but can't remember why it makes a difference...but have had problems before with inductive timing lights on these bikes and using a spare battery for powering the timing light fixed it

[rlvitt]

Thanks for the input guys. So long as my timing light shows the proper setting at the advance marks I pretty sure it's on the F mark at idle. I am going to try a second battery though. My spark advance seems very flexible and shows no sign of being stuck otherwise. I am centralizing my efforts on the Carbs at this point. I changed out all the jets and ploat valves. I put #40 idle jets in and dropped the main jet to  110. I had already dropped the needle to the top setting as advised by Hondaman. At this point I'm trying to make sure that the floats are operating properly. I'm noting a fuel overflow in the #1 and #3 carbs since the rebuild. I pretty sure that their levels are set properly at 25mm. I used a float gauge to check and adjust them if necessary. I am going to recheck their height using a clear tube off the float bowl drain to check the fuel level in the bowls.

Now here's a question that popped into my mind last night. I have the fuel tank feeding the carbs through am extended line from a shelf near the bike. The shelf is about 3 feet higher than the carbs. Could it be possible that there is too much "head" pressure from the elevation of the tank and that it might be forcing fuel past the float valves due to the pressure?

Thanks again for all teh advice and ideas. It is much appreciated.

Bob Vitt

[MCRider]

Thanks for the input guys. So long as my timing light shows the proper setting at the advance marks I pretty sure it's on the F mark at idle. I am going to try a second battery though. My spark advance seems very flexible and shows no sign of being stuck otherwise. I am centralizing my efforts on the Carbs at this point. I changed out all the jets and ploat valves. I put #40 idle jets in and dropped the main jet to  110. I had already dropped the needle to the top setting as advised by Hondaman. At this point I'm trying to make sure that the floats are operating properly. I'm noting a fuel overflow in the #1 and #3 carbs since the rebuild. I pretty sure that their levels are set properly at 25mm. I used a float gauge to check and adjust them if necessary. I am going to recheck their height using a clear tube off the float bowl drain to check the fuel level in the bowls.

Now here's a question that popped into my mind last night. I have the fuel tank feeding the carbs through am extended line from a shelf near the bike. The shelf is about 3 feet higher than the carbs. Could it be possible that there is too much "head" pressure from the elevation of the tank and that it might be forcing fuel past the float valves due to the pressure?

Thanks again for all teh advice and ideas. It is much appreciated.

Bob Vitt

I, and many racers and go-kart mechanics, etc, use an umbilical tank hanging from the ceiling for shop running the engine without the gas tank. No problems with pressure.

[rlvitt]

Thanks MCR. I've seen them but I don't know who sells them. I tried to fashion my own and it didn't work too well. Should've been a simple thing...... I dropped the tank height down to a more natural level and that seemed to reduce the head pressure. I checked the float levels with a clear tube and found the float levels all over the place. One fuel level was at 3-4mm from the top of the bowl and another's was 30mm from the top.  Time to start bending fuel valve tangs and get them adjusted right.

[Tintop]

I use an old plastic (no rust ) gas tank off a lawn mower.  Got it for free from my local small engine repair place off a junked mower.  Just need to add a something for a fuel shut-off tap.

[bear]

I use an old plastic (no rust ) gas tank off a lawn mower.  Got it for free from my local small engine repair place off a junked mower.  Just need to add a something for a fuel shut-off tap.

Great minds think alike Brian.
Use on myself.

Cheers,
Brian

[seanbarney41]

3-4 mm from the top is about right

[MCRider]

Thanks MCR. I've seen them but I don't know who sells them. I tried to fashion my own and it didn't work too well. Should've been a simple thing...... I dropped the tank height down to a more natural level and that seemed to reduce the head pressure. I checked the float levels with a clear tube and found the float levels all over the place. One fuel level was at 3-4mm from the top of the bowl and another's was 30mm from the top.  Time to start bending fuel valve tangs and get them adjusted right.

Mine is from MotionPro.
http://www.motionpro.com/motorcycle/partno/08-0032/

[Nic]

Here's my masterpiece, there's a Tee piece that goes from the single line to the two going to the carbs.

[rlvitt]

Damn! (Smacking myself in the forehead) I'd never have thought of that! Thanks. Got one.

[rlvitt]

3-4 mm from the top is about right

Then the 25mm float setting only deals with the bottom of the floats themselves...... I was thinking that the fuel level sitting that high (3-4 mm)would interfere with the emulsification of the fuel/air mix in the main or the mix in the idle jet.  I'll check the fuel stain lines on the floats themselves and see what the traditional distance from the top of the bowl the have ridden in the past. I'm thinking that it will probably be in that range. Thanks for the idea!

[Wobbly]

So it's a sure thing that the cam change means they need to be refitted for proper carburation.

No, it is not. I just put that cam into my bike and it started right up and runs perfect without any modifications.

[rlvitt]

I found that, among everything else, I had to lean out my mixture a bit. I had to drop the mains to 110's from 120's and dropped the needles to the top notch. However, I was also dealing with a stuck float, I think, which certainly didn't help the bike run. I changed the oil and it smelled like gas. I've got early 70's carbs and maybe they are a little more fussy due to the horsetail cable than the later models carbs. I dropped the fuel bowls and checked for the fuel height stains on the floats and they all showed it at about 5mm down from the top of the bowl. I put new gaskets in on two of the carbs and it seems to have taken care of the stuck float problem. It idles at about 1K pretty nicely now and gathers RPM's well. And the exhaust doesn't look nearly as black during a roll on. I believe that I should do one more carb adjustment if things remain OK just to see if I can get it running any smother at idle.