Any possibility of "bad" carb causing overheating?

[1man8scoots]

Sorry. I have 4 comp test kits sitting here, all 4 are shraeder valves on the threaded side.
The "new" guy bigwheeler has me on edge and I was hoping he'd just go away rather than continue ruining a thread where someone is asking for real help and he's giving bad information.
You need a better comp kit. A craftsmen, snap on, or mercury marine tester is the way to go.

[johnny248]

Sorry. I have 4 comp test kits sitting here, all 4 are shraeder valves on the threaded side.

Yeah, this one must just suck. I'm not sure what brand it is. I've had it for about 10 years, but it definitely has the valve on the gauge side. I guess I should invest in a new one to replace this.


It used to work fine, but after I got it back it hasn't been the same.

[1man8scoots]

I think they've recently within the past 5 years changed the design on comp testers due to the universal use of them.

[johnny248]

I think they've recently within the past 5 years changed the design on comp testers due to the universal use of them.

Not going to buy one from HF, that's for sure, but just one off the shelf from AZ or something ok? Or should I spend the extra cash on an OTC or something?

[1man8scoots]

I keep trying to help you because I want you to succeed not fail. Anything I suggest is something I would do myself.
I would recommend in using eBay for a new mercury marine test kit. Just don't buy a used comp test kit as you don't know how they have been handled. You need accuracy not hope it is right.
I've never yet allowed an engine to stay dead. I'm just as hard headed as any of us on here who is truly trying to tune or get an engine running. The main difference is, I work at a wonderful shop with a few extra hard headed geniuses to help.

[johnny248]

I keep trying to help you because I want you to succeed not fail. Anything I suggest is something I would do myself.
I would recommend in using eBay for a new mercury marine test kit. Just don't buy a used comp test kit as you don't know how they have been handled. You need accuracy not hope it is right.
I've never yet allowed an engine to stay dead. I'm just as hard headed as any of us on here who is truly trying to tune or get an engine running. The main difference is, I work at a wonderful shop with a few extra hard headed geniuses to help.

I appreciate your and everyone else help. Is this the guy you are speaking of?

http://pages.ebay.com/motors/link/?nav= ... 33&alt=web

[1man8scoots]

Alex with the rt mina ruckus build who just left yesterday has a well running engine now after the second rebuild. With his engine the first builder let it leave with over 180# of compression and air leaks everywhere. I spent near 2 hours changing the compression to a safe level and chased air leak after leak. You fix one and a new one would spring up. But you have to stay diligent and keep finding and fixing the leaks. In the end I got the comp to 125 ish with a .7 squish and zero air leaks. It held 5 psi in pressure for well over 5 minutes.
You more than likely have an airleak still. Even tiny little baby bubbles can screw up jetting. I took one guess at jetting on an engine that I had zero experience tuning directly and got jetting right the very first time. I can tune anything right as long as it's sealed properly and with proper compression.

Buy that compression tester!!! If you dont I am!

[johnny248]

I'll order that bad boy. No problems with clearance into the head being that it does not have a hose?

Even made in the USA. Nice

[1man8scoots]

Made in the USA is why I suggest it. Our standards of industry surpass most countries by far. I had one for many years and it dropped one too many times and became unusable. No clearance issues with mine on elites but depending on bike (spree, aero, etc) it may be harder to get into position to use or read. Great for off the bike use for sure. Works awesome on elites.

[Rip_City_Spree]

For reference on my Corsa Johnny even with my exhaust leak recently I was running a 108 MJ and a 35 pj and my bike wasn't overheating that badly and now I'm pretty certain my 108 is to high after I rectified the exhaust leak and put new gaskets in.

[1man8scoots]

Car tires do not have a lower pressure schrader valve than one used in a compression tester. Where are you getting your information from. The diameter of the valve, and it's core, dictate how much pressure it can hold. We used schraders in 15k psi applications.

[johnny248]

Let me just say one thing really quick about the valve core. I just purchased a new compression tester. Pulled out the valve core. The spring is less strong than a brand new pit of the box tire valve core. The tire core has a stiffer spring. The valve cores on tire valve stems are the same core regardless of it being a 60psi standard rubber stem, or a 200psi metal high pressure stem. Either way, the valve is holding pressure the opposite direction . so, unless the back flow is high enough pressure to physcially break the core, I don't see how it makes a difference.

Now, back to my bike. While waiting for the mecury tester to show up, I bought a new actron unit from AAP. I just did a cold compression test. carb installed, open wot, pod air filter installed. Held down the starter button until the pressure stopped climbing.


Assuming I can trust this new tester, it looks like I'm getting somewhere near 145psi.



Too high? Should I be addressing this from the base gasket since that is the place I sanded?

It currently has a fiber MHR gasket, which is still very thin, yet not as thin as the metal corsa gasket.

Should I try that 1/32" gasket that I made? Or should I address this a different way? I figure if the compression is too high, I would do what I need to do there before I move on to pressure testing.

[1man8scoots]

145 is fine, it's actually really good. 160 is kind of the threshold of octane, 170+ is a must. At 150 is where I start going 96 octane, but that's just me. You could get away with 160 with 93 but if you go lean your piston will go with it quickly. I'm at higher altitude than most and my compression ratio to air available is different than yours.
A lot of people like 120-130 psi for every day riders, which keeps it very safe, but that's too low for my riding style. 130 and it's new rings for me. If you want to lower your compression I'd go with head gasket shims rather than keep adding to the base. You will be raising your ports if you keep adding to the base. And soon you will have a very peaky and high rpm/low torque cylinder.

[johnny248]

Ok, then that changes things. If the compression look OK where it is, I will yank the motor and being pressure testing. I don't know why I was thinking you want to be around 120 psi with this, but it doesn't matter any more.

[1man8scoots]

120 is getting low on a vertical. It'll still run but it's not giving it it's all. Horizontals, some, are a whole other ball park, some can run as low as 90 and be considered good.