Kdx cooling system test with mityvac

[JZ05220r]

I was able to finally throw on a new oem headgasket to the kdx 220. I used my new mechanical torque wrench to criss cross tighten the cylinder head nuts in stages. I took a picture of the gauge pressurized to 14 psi before and after 5 minutes with bike off. There was a drop as you can see. I then did the running test and the needle is vibrating on the gauge. My god, this is just getting ridiculous. I swear im worried about ever touching another headgasket on any machine in the future at this point (I have went through numerous head gaskets and lapped the cylinder head trying to solve this issue) Not sure I’ll ever find out why because it just makes no sense to me. Very disheartening. https://youtube.com/shorts/NhxcP6uavA8? ... qxplNPFmnE

[Chuck78]

I've head of porous castings causing compression leaks into the cooling system in one KDX. Perhaps it's not a head gasket issue at all?

[Chuck78]

How do you have the mityvac hooked up?
Did you perhaps test the gauge itself, with a length of tubing plugged off on the end?

Post a photo of your gauge hookup, as I'm curious for my own testing purposes in the future.

I got a small pressure/vacuum gauge and 1/8 NPT threaded shraeder valve (tire valve) to make a 35mm intake pressure/vacuum testing adapter in conjunction with a rubber plumbing/freezeplug type expanding pipe plug in the exhaust. I could replace a coolant hose with a section of hose with a test tee perhaps, & use the same gauge setup minus the carb intake spigot adapter.

Have you tested your E-Series in this same way? Those bikes are the ones prone to overheating, not the H-series...

What grit of abrasive sheet did you use to true up the head and cylinder deck surfaces???

Best of luck, friend.

[JimmyB]

Might be worth trying(I know it is frowned upon) but might help for pressure testing for a head gasket leak and a brief test ride, coat both sides of the head gasket(even a used one) with a thin coat of some crankcase sealant or Permatex PermaShield # 85420, let it set up for 24hrs before trying anything.
I would be tempted to make up a plate( alloy or even plexiglass would work,you might be able to see the leak) in place of the head and pressure test both the cylinder and head separately to see if there might be a casting flaw, but I think I recall you might have tried replacing one or the other(maybe even both) and still have the same results??

There is a product you can use to find if it is combustion gases in the coolant.


Sorry to see you are having so much trouble with this bike.. :(

[JZ05220r]

How do you have the mityvac hooked up?
Did you perhaps test the gauge itself, with a length of tubing plugged off on the end?

Post a photo of your gauge hookup, as I'm curious for my own testing purposes in the future.

I got a small pressure/vacuum gauge and 1/8 NPT threaded shraeder valve (tire valve) to make a 35mm intake pressure/vacuum testing adapter in conjunction with a rubber plumbing/freezeplug type expanding pipe plug in the exhaust. I could replace a coolant hose with a section of hose with a test tee perhaps, & use the same gauge setup minus the carb intake spigot adapter.

Have you tested your E-Series in this same way? Those bikes are the ones prone to overheating, not the H-series...

What grit of abrasive sheet did you use to true up the head and cylinder deck surfaces???

Best of luck, friend.

I’ll send you pictures tomorrow. I have not tested the E series and don’t see the need as it’s running great and I had a good engine builder put it together. I used 220 grit and worked my way to 400. Thanks

[JZ05220r]

Might be worth trying(I know it is frowned upon) but might help for pressure testing for a head gasket leak and a brief test ride, coat both sides of the head gasket(even a used one) with a thin coat of some crankcase sealant or Permatex PermaShield # 85420, let it set up for 24hrs before trying anything.
I would be tempted to make up a plate( alloy or even plexiglass would work,you might be able to see the leak) in place of the head and pressure test both the cylinder and head separately to see if there might be a casting flaw, but I think I recall you might have tried replacing one or the other(maybe even both) and still have the same results??

There is a product you can use to find if it is combustion gases in the coolant.


Sorry to see you are having so much trouble with this bike.. :(

Great suggestions. However I’m probably going to switch up to a 200 cylinder and have the whole engine gone through. I plan to just run a pipe, and RB carb on it. I do recall on longer rides having some shifting issues between 1st and 2nd where I’d be stuck in gear for a second and would need the cases split to inspect and replace the corresponding transmission components. I’m 99 percent sure I could do the job myself but more comfortable having the entire thing gone through by a reputable person. Thanks

[JZ05220r]

How do you have the mityvac hooked up?
Did you perhaps test the gauge itself, with a length of tubing plugged off on the end?

Post a photo of your gauge hookup, as I'm curious for my own testing purposes in the future.

I got a small pressure/vacuum gauge and 1/8 NPT threaded shraeder valve (tire valve) to make a 35mm intake pressure/vacuum testing adapter in conjunction with a rubber plumbing/freezeplug type expanding pipe plug in the exhaust. I could replace a coolant hose with a section of hose with a test tee perhaps, & use the same gauge setup minus the carb intake spigot adapter.

Have you tested your E-Series in this same way? Those bikes are the ones prone to overheating, not the H-series...

What grit of abrasive sheet did you use to true up the head and cylinder deck surfaces???

Best of luck, friend.

Here’s your pictures. They are compression nut fittings.

[Chuck78]

Here’s your pictures. They are compression nut fittings.

Ahhh.... I see! You've got a special test port radiator cap... I wasn't interested in the mity vac hose fittings, I thought perhaps you spliced in a test tee in place of one of the KDX coolant hoses...

Is that a Mity Vac motorcycle specific radiator cap test fitting? That would be useful to have....

[JZ05220r]

Here’s your pictures. They are compression nut fittings.

Ahhh.... I see! You've got a special test port radiator cap... I wasn't interested in the mity vac hose fittings, I thought perhaps you spliced in a test tee in place of one of the KDX coolant hoses...

Is that a Mity Vac motorcycle specific radiator cap test fitting? That would be useful to have....

Yea it is the fitting that comes with the kit. I just ordered a 5/8” x 1/4” x 5/8” t fitting. I’m going to cap off one of the 5/8” inch ends, and connect the other 5/8” end to the spout on the cylinder head using a hose. Then I’ll connect the clear hose coming from the mityvac pump on the 1/4in section. I’ll cap off the spout coming from the water pump cover and then test on the bench.

I noticed the bike was running great, smoke free/few hesitations until about only a half hour. Then it start missing on the bottom and smoking heavily upon acceleration. Could I be blowing head gaskets? I was at 175 psi when compression testing. Im tempted to throw the stock cylinder head on that I just lapped on a surfacing stone.

[Chuck78]

I would go as far as heating up the cylinder off of the bike and removing the head studs as well, then check that with a straight edge, and lap that surface as well. I have seen on other bikes the studs pulling out slightly from the cylinder or crankcase, causing a bit of distortion on the gasket surface. This could be happening there and preventing you from torquing it fully.
And don't rule out a porous casting. After cleaning it up extensively, check every single area where there could be a pinhole in the casting that would leak crack case or cylinder compression into the water jacket areas.

[Chuck78]

Also, I just had another thought. Looking at base gaskets and used KDX cylinders on eBay, you could potentially leave the head attached to the cylinder as is without touching it, remove the cylinder from the engine after disconnecting the power valve linkage pressure test the cylinder / head / head gasket off of the bike with water or coolant to look for any wet spots of coolant / water indicating any leakage. That would tell you exactly where your problem is. You could also just air test it and use dish soap water or some other type of soapy solution in a spray bottle to spray down all areas involved and watch for bubbling like you do when testing natural gas or propane piping, tires and inner tubes, etc.

You could use a barbed tee hose fitting and a length of heater hose from the auto parts store with a couple of clamps and test it completely off of the bike. Then you could see where any water is trickling out or soap bubbles are forming. I definitely would use a liquid with some coloration to it.
Then depending on what you find, I would most likely go through the process of removing the head studs and resurfacing the cylinder head gasket surface as well as checking the head again. Also, checking the head stud threads.

Sorry you're having to suffer through all of this, but this is a learning experience for many of us watching you go at it, as well as our thought processes giving us New perspectives and potential troubleshooting procedures for our own future use or helping others out.
At least you have a good running E-Series! The 220's are my favorite KDX by far though, with the '86-'88 air-cooled power valve engines my second favorite.

[JZ05220r]

Also, I just had another thought. Looking at base gaskets and used KDX cylinders on eBay, you could potentially leave the head attached to the cylinder as is without touching it, remove the cylinder from the engine after disconnecting the power valve linkage pressure test the cylinder / head / head gasket off of the bike with water or coolant to look for any wet spots of coolant / water indicating any leakage. That would tell you exactly where your problem is. You could also just air test it and use dish soap water or some other type of soapy solution in a spray bottle to spray down all areas involved and watch for bubbling like you do when testing natural gas or propane piping, tires and inner tubes, etc.

You could use a barbed tee hose fitting and a length of heater hose from the auto parts store with a couple of clamps and test it completely off of the bike. Then you could see where any water is trickling out or soap bubbles are forming. I definitely would use a liquid with some coloration to it.
Then depending on what you find, I would most likely go through the process of removing the head studs and resurfacing the cylinder head gasket surface as well as checking the head again. Also, checking the head stud threads.

Sorry you're having to suffer through all of this, but this is a learning experience for many of us watching you go at it, as well as our thought processes giving us New perspectives and potential troubleshooting procedures for our own future use or helping others out.
At least you have a good running E-Series! The 220's are my favorite KDX by far though, with the '86-'88 air-cooled power valve engines my second favorite.

Those are great ideas, I may try that, I have got one more headgasket I’m willing to put on the line. I love the idea of testing the cylinder off the bike. I could test the water pump seal in a similar manner as well. But no coolant in transmission oil anyways. Thanks

[Chuck78]

Is that mityvac pump thays included with the coolant system pressure test kit, the exact same type of pressure/vacuum pump that comes with the brake bleeding vacuum pump kit? I wonder if I can just get by using my mityvac silverline pump and buying a few of the radiator cap and radiator cap pressure test fittings?

[bufftester]

Same pump, different adapters and accessories

[Chuck78]

Thank you, I'll have to price out the accessory adapters in this kit seperately. I had some pulled up originally but have since closed that search tab and cannot quickly locate them now outside of the full $60 kit woth the plastic pump.

[Chuck78]

Also, I just had another thought. Looking at base gaskets and used KDX cylinders on eBay, you could potentially leave the head attached to the cylinder as is without touching it, remove the cylinder from the engine after disconnecting the power valve linkage pressure test the cylinder / head / head gasket off of the bike with water or coolant to look for any wet spots of coolant / water indicating any leakage. That would tell you exactly where your problem is. You could also just air test it and use dish soap water or some other type of soapy solution in a spray bottle to spray down all areas involved and watch for bubbling like you do when testing natural gas or propane piping, tires and inner tubes, etc.

You could use a barbed tee hose fitting and a length of heater hose from the auto parts store with a couple of clamps and test it completely off of the bike. Then you could see where any water is trickling out or soap bubbles are forming. I definitely would use a liquid with some coloration to it.
Then depending on what you find, I would most likely go through the process of removing the head studs and resurfacing the cylinder head gasket surface as well as checking the head again. Also, checking the head stud threads.

Sorry you're having to suffer through all of this, but this is a learning experience for many of us watching you go at it, as well as our thought processes giving us New perspectives and potential troubleshooting procedures for our own future use or helping others out.
At least you have a good running E-Series! The 220's are my favorite KDX by far though, with the '86-'88 air-cooled power valve engines my second favorite.

Those are great ideas, I may try that, I have got one more headgasket I’m willing to put on the line. I love the idea of testing the cylinder off the bike. I could test the water pump seal in a similar manner as well. But no coolant in transmission oil anyways. Thanks

James - which one of the Mity Vac "small bayonet" radiator cap pressure test adapters fit our radiators? There's the MVA351 & the MVA352 (shallow). The 351 I might guess?????

[JZ05220r]

Also, I just had another thought. Looking at base gaskets and used KDX cylinders on eBay, you could potentially leave the head attached to the cylinder as is without touching it, remove the cylinder from the engine after disconnecting the power valve linkage pressure test the cylinder / head / head gasket off of the bike with water or coolant to look for any wet spots of coolant / water indicating any leakage. That would tell you exactly where your problem is. You could also just air test it and use dish soap water or some other type of soapy solution in a spray bottle to spray down all areas involved and watch for bubbling like you do when testing natural gas or propane piping, tires and inner tubes, etc.

You could use a barbed tee hose fitting and a length of heater hose from the auto parts store with a couple of clamps and test it completely off of the bike. Then you could see where any water is trickling out or soap bubbles are forming. I definitely would use a liquid with some coloration to it.
Then depending on what you find, I would most likely go through the process of removing the head studs and resurfacing the cylinder head gasket surface as well as checking the head again. Also, checking the head stud threads.

Sorry you're having to suffer through all of this, but this is a learning experience for many of us watching you go at it, as well as our thought processes giving us New perspectives and potential troubleshooting procedures for our own future use or helping others out.
At least you have a good running E-Series! The 220's are my favorite KDX by far though, with the '86-'88 air-cooled power valve engines my second favorite.

Those are great ideas, I may try that, I have got one more headgasket I’m willing to put on the line. I love the idea of testing the cylinder off the bike. I could test the water pump seal in a similar manner as well. But no coolant in transmission oil anyways. Thanks

James - which one of the Mity Vac "small bayonet" radiator cap pressure test adapters fit our radiators? There's the MVA351 & the MVA352 (shallow). The 351 I might guess?????

The correct one is the MVA321, just confirmed.

[kdxdazz]

did you end up solving this issue?

[JZ05220r]

did you end up solving this issue?

Hey, I gave up. I decided to throw another cylinder on the bike. Still waiting to have it all together.