Need help with chasing down an air leak

[freestylegeek]

Wow, that's some thin cases! I think you should add some kind of aluminium plate there. I added a 1 inch think T6 aluminium plate to the bottom of my cases to accomodate the 10mm. the machining went right thru the cases and into the plate. but it is leak proof! now:woot:

I'm ready for 12MM!!:brap:

It's interesting you say that Steve. Paul and I were contemplating doing that, but since it's "only" an 8mm stroker, we didn't see the need. I'm pretty much planning on the aluminum plate for any stroker motor I build in the future.

 

[ATS_Scott]

Read his post up there, he has already pulled the engine out, found the leaks, and repaired.

Yeah, thanks for your help. I was typing my post when the Wife found something better for me to do. Didn't get back to finish and post it till later. Next time I'll re-fresh so I don't upset anyone.

 

[freestylegeek]

Alright, more crap on this stupid thing. I won't go into details, but I've replaced 7 separate items that were the source of air bubbles when the engine was completely submerged in water and had 6 psi in it. Those items were:
1. pulse line fitting
2. gasket between reed cage and manifold
3. crack in bottom of cases
4. front crank seal
5. o-rings in head
6. lapped head and domes (they were slightly warped)
7. Exhaust manifold gasket (plus added some RTV for a slightly low spot on the manifold)

After all that, it STILL blows air bubbles out of the water outlets on the head. It's still leaking into the cooling system somehow. I found that the studs in the cylinder were spinning (not loctited) so I'll be cleaning those up and loctiting them in place. I was able to get 25 ft*lbs on them, but they would still rotate at that torque. I'm hoping it's just a simple case of the head not being torqued enough (due to the loose studs) and that will take care of it.

I'll be taking a straight edge to the cylinder to make sure it's flat also, but the chances of that warping are pretty stinking low.

As of right now, the Cleveland Rock N' Ride is questionable...:banghead:

 

[eel]

Porous cylinder casting at the transfer roof/roofs?

If you're getting bubbles with an Oring head @ 10psi, its not a warpage problem, unless you have about a milimeter of warpage.

It's a crack, grind through or porosity.

 

[eel]

I forgot, A quick and easy way to check cylinder castings for leaks is to spray soapy water (bubble bath is ideal) into the cooling jacket and blow the bejesus up the transfers, boost and exhaust ports with compressed air.

Also, "borrowing" a bit of bubble bath soap is a great way of introducing yourself to the milf neighbor!

 

[freestylegeek]

Along the same lines, could I find it by filling up the cooling pasages with mineral spirits and seeing where it is leaking through into the transfers/exhuast?

 

[Matt_E]

With a lighter. :biggthumpup:

Seriously, why mineral spirits?

 

[SuperJETT]

With a lighter. :biggthumpup:

Seriously, why mineral spirits?

Because it doesn't evaporate too quickly and won't damage anything inside.

 

[sjetrider]

I've heard of people putting an "H" in their fuel lines, and I wonder what effect that would have in the pulse lines too?

BTW, if anyone is wondering, my carb (dual 48 Novi's) settings are:

High - 100
Low - 115
N/S - 2.5
Spring 65g

WOW:bigeyes:that is seriously low pop off.

 

[freestylegeek]

OK, just took a close look inside under some REALLY good lights. The front cylinder has a deep vertical scar about 1/2 way up. It's got to be 0.015" deep at least (pictures to follow once I get home). That front piston also "rocked" more than the back one. So, time for an overbore. Cleveland is OUT for sure.

I did lap my exhaust manifold and I'm thinking the air leak was coming from the high spot on there. It was deeper than I thought, and I'm sure the metal gasket would not have filled it in. So, I fixed that problem, but then found the other. What do you do? Time to go to an 81.5mm bore. Maybe I can ride next year...

 

[freestylegeek]

Well, here's the carnage. I'm sure I need to go to 81.5mm or bigger.

 

[waterfreak]

Well, here's the carnage. I'm sure I need to go to 81.5mm or bigger.

that really sucks!:banghead:

BTW I just stuck a set of 48 Novis maxiflows on my 10mm set with
145 main
130 pilot
2.5 needle
115 spring pop off 20-21 lbs
I haven't tested the motor with this setting yet but it does sound pretty crispy on land:headbang:

 

[freestylegeek]

that really sucks!:banghead:

BTW I just stuck a set of 48 Novis maxiflows on my 10mm set with
145 main
130 pilot
2.5 needle
115 spring pop off 20-21 lbs
I haven't tested the motor with this setting yet but it does sound pretty crispy on land:headbang:

That's closer to what NOVI recommended to me. They said the 48's like 18-21 psi pop off. Once I get over this little top-end hurdle, I'll be trying that. Let me know how yours feels on the water, Steve.

 

[eel]

I've heard of people putting an "H" in their fuel lines, and I wonder what effect that would have in the pulse lines too?

That has pro's and con's in the fuel lines.

Tf you had a restriction in a fuel feed, ie. blocked filter, the carb could pull fuel from the unblocked side. But in a low fuel situation, ie. fuel surge from doing tricks, both carbs would pull air. Probably make FA difference in practice though.

I wouldn't "H" the pulse. The fact that one side is under + pressure while the other is under - pressure would tend to cancel each other out.

 

[freestylegeek]

Alrighty, now that I have a working ignition again, I can continue down the road to making this motor work right (It was a relaxing 3 month break <-- whole lotta sarcasm).

I thought I had eliminated the run-on condition just before the ignition died. The throttle wheel had a burr in it that would sometimes cause the throttle plates to only close to about 1/16 throttle. I was just getting started verifying the fix when the ignition died. So, tonight when I fired it up, everything was great. It idled nicely, and revved up to lower RPMs well. I gave it a good two full throttle stabs, and it never came down. I hit the stop button, and nothing happened, so i pulled the throttle and shut it down. The motor passed the air leak test from the carb base to the headpipe mount (6 psi for 25 minutes), so I KNOW there is not an air leak in the motor. It has to do with the carbs somewhere... I just don't know what. Throttle plates are good, shaft seals are good, jetting is good, return restrictor is good, what else can be checked?

 

[Matt_E]

How long did you idle the motor? The fuel lines may have had some air in them.

If it is indeed an airleak problem, it will be below the throttle plates. Check you carb gaskets?

 

[freestylegeek]

How long did you idle the motor? The fuel lines may have had some air in them.

If it is indeed an airleak problem, it will be below the throttle plates. Check you carb gaskets?

Idled for a good 30 seconds before the full throttle bursts. Carb gaskets are new, but not the 'green' style. However the last time I put the carbs on I used plenty of grease on both sides of the carb gaskets.

 

[Big Kahuna]

Hey Matt, check to see that both butterfly Plates are closing all the way, I have seen where one is not all the way closed causing this... Happend to Chris (buddy of mine), I was working on his ski with some Blackjacks, could not figure out why it running away...finally thought to check that....... it could be something that simple.........

 

[freestylegeek]

Hey Matt, check to see that both butterfly Plates are closing all the way, I have seen where one is not all the way closed causing this... Happend to Chris (buddy of mine), I was working on his ski with some Blackjacks, could not figure out why it running away...finally thought to check that....... it could be something that simple.........

I checked that too Harrison. both plates are perfectly synchronized, and closing all the way.

 

[Big Kahuna]

hmmmmmmmmmm..... turn the forced plenum x5555666.2 air induction system off....................

This is a weird one.......... crack in the carb bases?????? hard to see how the carbs could cause this short of the air adjustments or jetting being lean........ have you tried upping the low speed jet? I know, sounds trivial, but I think that is what you are going to find......... (something so simple)