50mm BBK + A9 Cam = tooth off? Let's find out!
May 10, 2015 10:35:55 GMT -5
kkzxxx, Upgrayedd, and 2 more like this
Post by Silar on May 10, 2015 10:35:55 GMT -5
DISCLAIMER: This is a test I performed knowing the risks. Do not attempt this if you do not accept the risk of possible engine damage. Also.. Do not attempt this without having the proper tools and about 10 to 12 beers in you so you have a nice buzz, because without the buzz, I would have never even tried it.
Something that has bugged me a bit since I put the 50mm BBK and A9 cam in is that TDC (according to the cam) was at or slightly before the actual 'T' letter on the flywheel and not on the 'T' line. I've always wondered if I've maybe got it a tooth off but was more afraid of damaging the engine. My scooter runs pretty darn good I have to say but there has always been something just not right. It's a bit hard to start and doesn't have the oomph I'm thinking it should have. Also, when I've got the throttle cranked WOT, I hear a slight low rumbly gurgle sound. It's really hard to explain, but almost like a bogging sound, but It's not really bogging.
I've learned so much by working on this scooter and using these forums, and I know the 'just not right' that I'm experiencing isn't variator, clutch, carb, or lower engine or final drive gears.
As a test, I thought.. What the hell. At the most I'm going to do is maybe bend a valve, bust a piston, destroy my crank/bearings/rod... Maybe have to buy a new BBK.. Hell, maybe have to buy a whole new engine! But I thought.. for the sake of my sanity, all great people of the world, and so I can finally rule out that ever so slight possibility that my scooter's timing 'T' line wasn't correct, I had to try.
Soooo.. I decided last night to set my cam a tooth off. Once I made the change and when the cam was at TDC (holes level with the head), the timing indicator was directly on the 'F' mark. Yikes! That was way more than I expected for just one tooth! But.. I remember a thread where someone else mentioned that their TDC was at the 'F' mark so I thought may my engine is similar..
I also decided to go ahead and adjust my valves to both .002 while I was at it.. I originally had them at .002 intake and .003 exhaust, but the exhaust valve seemed to tick way to loud.
I put everything back together and fired it up making sure to keep my finger on the kill switch just in case something went horribly wrong. I just ran it last night on the stand to make sure everything works but it was way to late and I had way too many beers in my to even chance it. I decided to take it for a spin this morning.
All I can say is I cannot even explain how much better my scooter is. I've had a lot of trial and error with this scooter, but this change was the obvious answer to my 'just not right' issue. It sounds better when starting up, it sounds amazing when riding. The throttle response is super fast and snaps back at the blink of an eye. No more revving the engine to WOT then watching the tach needle drop below idle for a second or two then back up to idle. And the weird rumbly gurgle sound at WOT is gone. Torque seems about the same and I've not checked top speed. It's never really been about top speed for me though, just want to keep up with local town traffic and climb the hills.
A strange side effect of this: I had to adjust my idle/fuel screw clockwise (closing) to get the best idle.. I did not expect that.
I am still running my stock CDI with this setup. I may put the blue racing CDI back in to see how it does with that also.
My scooter just sounds right now... almost like the engine is happy.
HumanShield, I don't have a big valve head but I'm not far behind you!
Brent and all else, I now see how addictive these little scoots can be, especially for people that are more tech savvy and like to tweak.
Something that has bugged me a bit since I put the 50mm BBK and A9 cam in is that TDC (according to the cam) was at or slightly before the actual 'T' letter on the flywheel and not on the 'T' line. I've always wondered if I've maybe got it a tooth off but was more afraid of damaging the engine. My scooter runs pretty darn good I have to say but there has always been something just not right. It's a bit hard to start and doesn't have the oomph I'm thinking it should have. Also, when I've got the throttle cranked WOT, I hear a slight low rumbly gurgle sound. It's really hard to explain, but almost like a bogging sound, but It's not really bogging.
I've learned so much by working on this scooter and using these forums, and I know the 'just not right' that I'm experiencing isn't variator, clutch, carb, or lower engine or final drive gears.
As a test, I thought.. What the hell. At the most I'm going to do is maybe bend a valve, bust a piston, destroy my crank/bearings/rod... Maybe have to buy a new BBK.. Hell, maybe have to buy a whole new engine! But I thought.. for the sake of my sanity, all great people of the world, and so I can finally rule out that ever so slight possibility that my scooter's timing 'T' line wasn't correct, I had to try.
Soooo.. I decided last night to set my cam a tooth off. Once I made the change and when the cam was at TDC (holes level with the head), the timing indicator was directly on the 'F' mark. Yikes! That was way more than I expected for just one tooth! But.. I remember a thread where someone else mentioned that their TDC was at the 'F' mark so I thought may my engine is similar..
I also decided to go ahead and adjust my valves to both .002 while I was at it.. I originally had them at .002 intake and .003 exhaust, but the exhaust valve seemed to tick way to loud.
I put everything back together and fired it up making sure to keep my finger on the kill switch just in case something went horribly wrong. I just ran it last night on the stand to make sure everything works but it was way to late and I had way too many beers in my to even chance it. I decided to take it for a spin this morning.
All I can say is I cannot even explain how much better my scooter is. I've had a lot of trial and error with this scooter, but this change was the obvious answer to my 'just not right' issue. It sounds better when starting up, it sounds amazing when riding. The throttle response is super fast and snaps back at the blink of an eye. No more revving the engine to WOT then watching the tach needle drop below idle for a second or two then back up to idle. And the weird rumbly gurgle sound at WOT is gone. Torque seems about the same and I've not checked top speed. It's never really been about top speed for me though, just want to keep up with local town traffic and climb the hills.
A strange side effect of this: I had to adjust my idle/fuel screw clockwise (closing) to get the best idle.. I did not expect that.
I am still running my stock CDI with this setup. I may put the blue racing CDI back in to see how it does with that also.
My scooter just sounds right now... almost like the engine is happy.
HumanShield, I don't have a big valve head but I'm not far behind you!
Brent and all else, I now see how addictive these little scoots can be, especially for people that are more tech savvy and like to tweak.