Dropped A Valve! By gy6ownsall (Read 682 times)

[gy6ownsall]

So the 2009 Velocity 150 I bought for next to nothing dropped the exhaust valve about a week ago. Not surprised. Scoot had 4xxx miles, that being said, after going through every corner of the scoot during the troubleshooting phase of trying to figure why it wouldnt run past 30mph, I came to find out the air filter in the air box was shot. Like an idiot, I removed it. "Its running fine" i told myself, and it actually really was, then a slight backfire on deceleration began to develop. Until 1 night around 40mph, she suddenly gave out. I Pulled over, pulled the spark plug, the bottom was CRUSHED. Good thing I have a good sense of humor! I laughed and ordered a stock motor from a scooter parts dealer a few miles from my home. Im thinking of doing a CHEAP "no machining or boring" big bore kit to the motor I dropped a valve on. Any recommendations? Ebay seems to have some decently cheap price full kits.

[frmrwiseguy]

At what rpm did you drop the valve?

[gy6ownsall]

Aug 23, 2013 19:50:53 GMT -6 frmrwiseguy said:

At what rpm did you drop the valve?

Maybe 7-8k rpms, I want a 61mm big bore kit that requires no more machining or boring.

[frmrwiseguy]

Did the valve break and if so were?

[Alleyoop]

Yes running them lean causing backfires will damage your exhaust valve. In your case it dropped it which causes more damage. Some get lucky and just burn them bad.
Alleyoop

[frmrwiseguy]

Do they bust the valve head off or blow the keepers out of the retainer?

[gy6ownsall]

Aug 26, 2013 13:45:25 GMT -6 frmrwiseguy said:

Did the valve break and if so were?

Mine broke off about half way down the stem

[frmrwiseguy]

Thanks.
Ahhh the weak link.
A lean condition will not cause the break mid stem.
I will be making some Forged Titanium valves this winter.
Plasma coated of course.
Thanks again!!

[Alleyoop]

Yea got to watch running the motors lean they get really hot and if the metal is not up to par things break.
Alleyoop

[gy6ownsall]

Aug 27, 2013 14:39:39 GMT -6 Alleyoop said:

Yea got to watch running the motors lean they get really hot and if the metal is not up to par things break.
Alleyoop

Finally got my cheap 61bbk in, waiting for machine shop tomorrow...The head appears to be a completely stock head matched to 61mm. Wont I be going backwards as far as building for more power with stock intake/exhaust valves, port diameters, stock carb and exhaust?

[Alleyoop]

BBKs give you more low end torque not necessary any more top end. You will get up to speed much quicker cause it will have more power to pull the weight. Free Flow Exhaust and Free flow filter with a BBK will help the motor make more power. You currently have a 24mm carb which is plenty don't worry about it. You will have to up jet at least the main jet. I have a 62bbk with a 60mm stroker crank and I am arunning with a #38 Pilot jet and a 122.5 Main jet in my 24mm carb. It will run with a 120 main jet but I rather be on the save side and be a little rich on the top end. But with my setup I very rarely run it WOT because of my taller gears and since it is a Trike Bigger Rear tires I get up to speed really quick and then back off the throttle and it will hold 50mph at 5100 rpms and 60mph at 6100 rpms. That is about what I run around here.

So In your case I would start with a #120 Main and see how it runs with that. You do not want to run with what came with the carb which range anywhere from 103-107 main and a #35 Pilot jet.

When you run it vary the speeds and do not crank it up WOT for long periods of time until you put some miles on it.
Also listen if the motor makes different sounds when riding it around at different speeds. If the motor needs something either more fuel or less fuel it could make different sounds on throttling up, at WOT and or letting off the throttle.

Let me know how it goes and listen to your motor.
Alleyoop

Here is my carb setup:

[gy6ownsall]

Aug 27, 2013 21:51:25 GMT -6 Alleyoop said:

BBKs give you more low end torque not necessary any more top end. You will get up to speed much quicker cause it will have more power to pull the weight. Free Flow Exhaust and Free flow filter with a BBK will help the motor make more power. You currently have a 24mm carb which is plenty don't worry about it. You will have to up jet at least the main jet. I have a 62bbk with a 60mm stroker crank and I am arunning with a #38 Pilot jet and a 122.5 Main jet in my 24mm carb. It will run with a 120 main jet but I rather be on the save side and be a little rich on the top end. But with my setup I very rarely run it WOT because of my taller gears and since it is a Trike Bigger Rear tires I get up to speed really quick and then back off the throttle and it will hold 50mph at 5100 rpms and 60mph at 6100 rpms. That is about what I run around here.

So In your case I would start with a #120 Main and see how it runs with that. You do not want to run with what came with the carb which range anywhere from 103-107 main and a #35 Pilot jet.

When you run it vary the speeds and do not crank it up WOT for long periods of time until you put some miles on it.
Also listen if the motor makes different sounds when riding it around at different speeds. If the motor needs something either more fuel or less fuel it could make different sounds on throttling up, at WOT and or letting off the throttle.

Let me know how it goes and listen to your motor.
Alleyoop

Here is my carb setup:

Cool, Im worried about alot to be honest, Im also waiting on 12g roller weights, a Kevlar belt and a 16/36 gear. Hopefully putting the motor back together tomorrow!

[frmrwiseguy]

The weak link on any valve is were the Stem meets the head.
I would think if it got that hot to break the stem mid way up, the temper was also taken out of the piston.
I'm thinking these lame break in procedures for stock or bbk is due to Dino rings and not a final finish with a Plateau hone of 400-600 grit.
A much better ring seal can be created with a good set of modern rings and the Plateau hone preferably with torque plates.
then you can break it in like you stole it.
btw yoop very nice carb set-up!!

[frmrwiseguy]

Yoop.
Off topic here but what did the bbk kit come up with as far as a squish clearance?
Would imagine all these cylinders stock or bbk have different heights.