float height

[speedyts49]

I am trying to cure a new problem of over reving at start-up. Also when I twist the throttle the engine revs but does not want to come back down to idle speed imediatly, it kind of lingers. With the engine off I can hear the slide snap back down in the carb when I release the throttle so I don't think it is my cable.
Things I've done since the bike was running near perfect;
1. a new piston and rings plus 607 reeds(it ran great after that) for two hours.
2. sheared a woodruf key and the bike died.(did not know it at the time)It make a really loud clacking sound when I restarted it.(pulled the cylinder thinking I had done a hack job on the top end but it looked good, turned out to be the key was missing!
3. Pulled the carb a number of times before I found the missing key. I also adjusted the float height a little to make 16mm. its about 15mm now. As a mater of fact I did not think it really changed even when I bent the tang.
4. After all of this I started it and like I said it revs real high and then when I twist the throttle it boggs OR revs normal but does not return to idle speed right a way.

I have added a photo to see if you all think i am taking the measurement right. I take it from the tip of the float. Is this correct?
thanks,
tom

 

[jaguar]

Sounds like you have a bad seal allowing unwanted air into the engine.
If there's a lot of black crud in your ignition cover then its the left crank seal.
Is your carb boot (closest to the engine) in good condition or does it have cracks?
How's your engines head gasket? Could of blown it with the excess pressure of igniting the fuel/air mixture very advanced (which may happen one or more times when you shear the woodruf key. I sheared a couple until I used an abrasive paste to wear down the shaft and flywheel where they meet so that they match perfectly. Just put some on the shaft and then put the flywheel on (without the nut) and then press lightly while rotating the flywheel.

 

[speedyts49]

I don't have any crud in the ignition side. The carb boot and all the gaskets are brand new. I also replaced the ignition coil and then realized it was not bad once I learned how to use my AUTORANGING multimetter. Duh.
Could not having the seat on allow too much air? I have not put it back on because I have had to pull the carb so many times trying to sort out the problems.
So you think i am getting too much air in the engine maybe. I will look into that today.

155 main changed to a 150 , 48, stock needle middle position, stock pipe. '93kdx200 2800 miles
thanks,
tom

 

[speedyts49]

I rechecked the float height, carb, reeds, and changed the pilot to a 45. The compression is 160psi which is good. I pulled the LSC off to check for black crud but found none. I still find what seems like a lot of gas in the intake boot and behind the reeds. Maybe thats normal, don't know.
To check for a leak am i supposed to use wd40 and spray around the intake boot and head gasket with the bike running? Are there any other areas to check or sprays to use? Then will I see bubbles or hear the motor run funny if there is a leak?
I have the air screw at 1 1/2 turns out. Its hard to adjust because of the surging etc.
tom
(i'm the one that smells like high test)

 

[wibby]

Have you read the article in Tech Tips for adjusting float height?

Reason I ask, you would not be able to measure float height with the carb upside down as shown in your pic.

 

[JCW]

A high idle setting can cause the high RPMs plus the delay in dropping to idle after you let off of the gas. Also, reducing the size of the pilot jet will cause a definite increase in crank and idle RPMs. I would drop the idle setting and see if the delay in returning to idle speed stops. I had to back off of the idle screw after changing from the 48 to the 45. I would back it out 1 full turn, crank the bike and let it warm up, and then set the idle. Hopefully, that will solve your problem.

Good Luck,
JCW

 

[speedyts49]

Yes thanks I read the float height tips and I have a manual so I think it is ok. I should end this thread and start a new one perhaps on surging revs/bogging.
JWC,
I turned the idle completly off and used the throttle to keep the bike running but it would rev without me twisting the throttle.
I have not really let the bike run too long becuase I am afraid I have a air leak causing a lean condition and don't want to seize the piston.
I also rechecked the coil and it is good.
I have a new head and lower gasket so it shouldn't be sucking air but you never know.
tom

 

[speedyts49]

If I find that the head gasket or the carb intake boot is sucking air is there a liquid gasket seal I can use? Also I have read some posts thru the search function that say I can fix a crankseal leak using JBweld. Starter fluid seems to be the spray of choice for finding leaks.
talk to me.
tom

 

[pketchum]

You have the classic symptoms of an air leak that was certainly introduced when you performed your recent maintenance. The ONLY way to really get to the heart of the problem would be to fabricate a "leak down tester" so you can pressurize your engine (closing the exhaust port, introducing air through the rubber carburetor manifold. You should be able to hold 6psi for at least 1 minute. For instructions on how to build one of these see: http://www.westcoasthodaka.com/psitst3.html

For a pressure guage don't look for a low pressure gauge but instead look for a vaccuum gauge. Instead of a fuel petcock I used some brass T-valves I found at an ACE True Value store in my neighborhood.

I wouldn't worry too much about running the bike at an idle or above with an air leak but don't get it too hot by racing it, or riding it hard, because you may seize the engine. I pressurize the engine, then spray soapy water from a spray bottle on all intake gaskets, base gaskets, head gaskets, intake manifolds, exhaust manifolds, spark plug, cylinder studs, magneto seal, clutch side seal (if I have the clutch out), and also on the case halves. I've seen leaks in weird places like once I found a air leak that was caused by a casting flaw in the barrel that had come from the factory.

I build my own Hodaka race engines several times a year and I'd be lost without my leakdown tester. It's the ONLY way to be sure that you've sealed your engine properly!

Good luck!

 

[JCW]

JB Weld would be fine on metal or cast parts (after they are cleaned with contact cleaner and scuffed up for good adhesion). I would not use it on the rubber intake gasket if that happens to be the problem. Regarding rubber leaks, my first choice is to buy a new part. However, if you clean the part with contact cleaner and use a high temp silicone, you could seal the leak and confirm the problem. From what you are saying, it sure sounds like an air leak. Could there be a broken gasket on the intake manifold (carb side or engine side) ?

Good Luck,
JCW

 

[pketchum]

Sometimes you can crank down on the intake manifold too much and actuallycause a warp which creates the air leak. Suggest that you break apart what you've removed and use a smidgen of Yamabond or Kawasaki equivalent in addition to the new gaskets you have installed. The lone exception would be the head and base gaskets. You should use something that's hi-temp approved in these areas.

Phil Ketchum

 

[speedyts49]

Today I put some pematex gasket sealer on the intake boot and a small bead on the head. I did not put any on the cylinder itself though. I decided to wait 24 hours to let the Permatex set before retrying the bike. I also re-cleaned the carb while I had it off and made certain nothing was wrong with the kips.
I will look at the leakdown tester you mentioned and see if I can make one.
I found one nut on the cylinder body that was a little loose. I don't have the correct tool to torque those nuts(not enough room). Maybe a crow foot?
Thanks for your input,
tom

 

[pketchum]

Tom,

You can e-mail me directly if you're having any problems constructing a leak down tester. I haven't had the need to adapt my leak down tester that I use on my Hodaka's for my KDX 200 yet but I'm sure that they will come a time.

For my Hodaka's I have to make adapters for the different exhaust configurations, i.e. for the 71 Super Rat I use a length of old two-ply bicycle tube and a hose clamp and cinch it down. Pressurizing the crankcase to 6psi causes it to bulge like a balloon. For the Super Combat and Combat Wombat's which use a completely different exhaust manifold, I use a piece of 1/8th" thick rubber gasket and COMPLETELY cover the exhust port, then install and bolt down the exhaust manifold, sealing the exhaust completely. Once I tried to start the engine, not realizing that I'd forgotten to remove this seal and had a difficult time figuring out why it sounded so muffled. <grin>

One the intake side, I buy PVC caps that have an OD diameter the same, or close to, the rubber intake manifold. If they're close, I use my bench grinder to grind them to the approximate OD as the ID of the rubber manifold. Then I buy a Schraeder valve used on big trucks from NTB (National Tire and Battery) and drill the PVC cap and install the air valve, and insure that it has an airtight fit. The air valve that I'm referring to has threads and a nut that you can use to cinch it down. I've used regular all rubber air valves before too but you have to closely match the valves size to the hole you're going to drill into the PVC cap so that you'll be assured of an airtight seal. Then I remove the innards of the air valve. To pressure test, seal up the exhaust, remove the carb, install your custom PVC cap where the carburetor was, cinch it down, attach your hand operated air pump to the PVC caps air valve and slowly pressurize to 6psi. Don't overpressurize the crankcase or you run the risk of blowing either one of your crank seals. Presurize to 6psi and see it it will hold it for at least 1 minute without dropping to 5psi. Spray soapy water around everything looking for bubbles. Where you see bubbles you've to an air leak. Often I've found up to 3 air leaks in an engine even when using new gaskets all the way around. I've always found that surprising, so I go back and use Yamabond in these areas or hi-temp sealant on the head or base gasket. I always try to get them to seal without using this since it makes rebuilding more difficult then next time around since you have to work harder to remove the gasket material since it's BONDED really well.

Phil Ketchum
Moderator, Hodaka Owners Group
http://groups.yahoo.com/group/Hodaka
'94 KDX 200 (new owner, no experience)

 

[speedyts49]

Originally posted by wibby
Have you read the article in Tech Tips for adjusting float height?

Reason I ask, you would not be able to measure float height with the carb upside down as shown in your pic.

Your right! I forgot to tilt the carb as described in the tech tips. I was looking in the service manual and I did not see or read anything about tilting. I have a feeling I will get another chance to check it real soon.
thanks,
tom

 

[canyncarvr]

Ensure the throttle cable retainer (the white nylon piece) is properly seated in the slot of the nut. It's easy to miss seating the nylon tab in the slot.

That will get you an unstable idle....not surging.

Sounds more like a leak.

 

[speedyts49]

I built a leak down tester today per Phil's instruction. I found the leak to be at the rear on the cylinder base. When I removed the reed cage I saw the piece of gasket that should of been under the cylinder flapping in the wind. The part has been ordered(again).
I used a 2" test stopper, a couple of pieces of pvc, an old innertube valve and my bike pump. The exhaust port is 1.8" and the intake boot is around 1.6" so the plumbing supplys worked pretty good.
thanks all,
tom :)

 

[JCW]

Speedy & pketchum,

Thanks for the info and photo. What a neat way to test for leaks. I hope I won't ever need it, but I know what to do now if I have a leak I can't find. BTW, is your bike well again?

JCW

 

[speedyts49]

I had to order another gasket which takes a couple of days to get from the dealer. From the air I could feel with my hand I can't believe it ran at all.
Once I get it all back together and check it out for other leaks, you never know, then I will take the leakdown tester apart and show it in more detail.
thanks,
tom

 

[speedyts49]

It was an air leak. I got a new base gasket yesterday and put it all back together today and it runs great.
The picture I put on a previous post is not the correct way to build a vacuum gage although It helped me identify where the leak was. Phil has sent me a photo of a vacuum gage that he uses. I plan on completing mine in the future(before the next top end anyway).
thanks for the help.
tom