Blaster Not sure what went wrong

[Dre0256]

Just got done building my son's B1, 701 Riva red pipe, Riva girdle head (35cc domes), wetjet 46mm carb/intake, a/m water box (triton I think). Ok compression 185 psi, fire fuel all good. Took out to water test, kept on cutting off. Replaced check valve on tank and put new plugs. Ran better but kept on cutting off to the point where it would not start. Took home checked over, front plug was loose and lost compression in the front cylinder down to 40 psi. So two problems obvious loos of compression and keeps cutting out like its running out of fuel. When it would shut off, it would start right back up until it did not any more. Would the loose plug cause it to run lean? Thanks for any help.

Dre

 

[WFO Speedracer]

It was cutting off because the engine was seizing up, air leak would be the most likely culprit, lean fuel mixture a close second.

 

[Dre0256]

Any particular location where air leak might be a common place?

 

[WFO Speedracer]

intake gaskets are prime leak canidates on 61X engines

 

[Dre0256]

Well am pulling motor out tom and see the damageand go from there....frustrating...:aargh4:

 

[WFO Speedracer]

Do a pressure test on the engine before you disassemble it, otherwise you may never know what happened.

 

[Dre0256]

Now correct me if am wrong in order to do the compression test on the engine I need to close the exhaust & intake ports and preassurise through the intake vent, keeping plugs in place?

 

[WFO Speedracer]

Yes exactly, it should not leak more than a lb per minute, I usually go for 10-15lbs of pressure

 

[Dre0256]

So just take carb off and make block of plates for intake and exhaust side?

 

[WFO Speedracer]

Yes you can make them fror old inner tubes or sheet rubber using the carb and exhaust as the block off plates, slip the rubber pieces in there and bolt the head pipe and carb back on.

 

[Dre0256]

Oh ok thanks, I was actually thinking of making like a metal block off plate, but wow rubber pieces much easier. Thanks for the help bro.

 

[QuickMick]

You can add your pressure through the pulse line, along with a gauge.

 

[Dre0256]

You can add your pressure through the pulse line, along with a gauge.

Yea am planning on using the pulse line and hook my mikuni popoff gauge

 

[Dre0256]

Ok so I blocked the engine off with pieces of inertube as sugested. I pumped the engine up to 10 psi and it held for 30 minutes no problem. Took top end off and front rings were completely stuck in and rear piston had sings of where it would had or was on its way to also seize. When I build the motor to begin with I had a regular 46mm with a regular yami intake, but it was not running right from the get go so I changed it and put the wetjet 46mm carb and intake. I know the wetjet carb and intake is fine since I took it off a running motor. I had also noticed that the reeds were kinda open on the 1st carb/intake set up I had on. So what am I looking at? I have a whole other top end (cylinders w/pistons) so thats not an issue.However I don't want to put on and have same result.

 

[FlightPlanDan]

I'm not being a smart-ass , but this happened to a friend of mine. He had installed the pistons 180 out. (arrows pointing toward intake). Just a thought.
It would run for a bit.... similar symptoms.

 

[Dre0256]

I'm not being a smart-ass , but this happened to a friend of mine. He had installed the pistons 180 out. (arrows pointing toward intake). Just a thought.
It would run for a bit.... similar symptoms.

Yea no problem but no arrows pointed to the exhaust side, but thanks tho.

 

[WFO Speedracer]

Did you have this bored when you put it together, improper clearance maybe, it ran way lean or way too hot.

 

[Dre0256]

Did you have this bored when you put it together, improper clearance maybe, it ran way lean or way too hot.

Yes it was bored, but it was already done when I got it.

 

[WFO Speedracer]

Yes it was bored, but it was already done when I got it.

Just wondering if it had adequate clearance,this is exactly what happens when the clearance is too small, piston grows larger than the bore its supposed to fit in then boom, no compression.

 

[Dre0256]

Well I got another top end w/cylinders that I know are good. Ran it for like 10 hrs then went to something else. It was in my X2 701 conversion ski, so I know its good. Will bolt that on this afternoon and try again. Thanks for the help so far.

DRE