Top speed dropped from 43mph to 35mph

[NOLA Rider]

I've been struggling with my top speed loss lately and I thought maybe someone could advise me since I'm not expert:

I have an upgraded engine but can't remember the model (needle bearings, CNC head, but no porting or anything crazy) with a shift kit, CNS carb, and Jaguar CDI. After getting to 43mph and realizing I wanted to live, I enjoyed cruising around New Orleans around 35-38mph until my carb starting acting up. Turns out the C clip had worn away the space on the pin and moved around too much. Since I had used it for a good few years, I decided to upgrade to a Dellorto 15.15 (genuine) carb. As I was jetting my new carb, the Jaguar CDI died on me so I just put on my spare stock CDI. Now carb is jetted properly (light brown on spark plug) but I can't get even close to 40mph. Bought a BBR CDI since I can't find anyone selling a Jaguar CDI hoping it would help, but I'm stuck at 35mph. I even repaired the CNS carb by using some JB Weld, but no improvement.

Any thoughts?

 

[mony0_3]

My top speed dropped on a couple of my faster bikes by about 8mph last year. I think maybe something with the fuel blends. I also had to change from 70 to a 65 jet to stop four-stroking.

 

[Karl Snarl]

I've been struggling with my top speed loss lately and I thought maybe someone could advise me since I'm not expert:

I have an upgraded engine but can't remember the model (needle bearings, CNC head, but no porting or anything crazy) with a shift kit, CNS carb, and Jaguar CDI. After getting to 43mph and realizing I wanted to live, I enjoyed cruising around New Orleans around 35-38mph until my carb starting acting up. Turns out the C clip had worn away the space on the pin and moved around too much. Since I had used it for a good few years, I decided to upgrade to a Dellorto 15.15 (genuine) carb. As I was jetting my new carb, the Jaguar CDI died on me so I just put on my spare stock CDI. Now carb is jetted properly (light brown on spark plug) but I can't get even close to 40mph. Bought a BBR CDI since I can't find anyone selling a Jaguar CDI hoping it would help, but I'm stuck at 35mph. I even repaired the CNS carb by using some JB Weld, but no improvement.

Any thoughts?

Have you tried retarding the timing slightly, also making sure your squish is set around .7-.8. I never used a jag cdi, I can get the same results for the cost of a star washer and a flat washer. Ten cents vs $175 is a no brainer for me. I use " catnip" cdi's. I can't tell you where my timing is, because well I just been doing it by feel. Next engine I will know, I'm building a mini hybrid. I use saw carbs and a g2 reed, with stuffer, although I hear the sha carbs are really good. Can't imagine it's your carb, maybe jetting but carb should easily support 50 on our rides.

 

[Greg58]

It takes some time and is tedious work but making an offset key for the magnet can retard timing, you can compare several magnets for the keyway location some are cut different.

 

[NOLA Rider]

Thanks everyone for the input, everyone. I will definitely play with the fuel mix first to eliminate that as a suspect. Concerning adjusting the timing, shaving down the woodruff key would retard it, yes? Also, if this does help, would it prove the time has been off this entire time?

 

[Karl Snarl]

Thanks everyone for the input, everyone. I will definitely play with the fuel mix first to eliminate that as a suspect. Concerning adjusting the timing, shaving down the woodruff key would retard it, yes? Also, if this does help, would it prove the time has been off this entire time?

shave the clockward ( the way a clock ticks towards the right side, when facing the engine magneto side) side to retard. you will be moving the magnet counter clockwise how many ever degrees.

 

[Karl Snarl]

It takes some time and is tedious work but making an offset key for the magnet can retard timing, you can compare several magnets for the keyway location some are cut different.

Belt sander and a pair of pliers. Takes all of 30 seconds. lol. I have a 36" strip sander belt sander. So easy to just slap up, push and bamb I'm done.

 

[Greg58]

I don’t have it at home but at the previous job we had a brooch set to cut a keyway in any hub, I could cut the keyway in the magnet to what I needed to retard the timing, it never occurred to me to do it.

 

[Karl Snarl]

I don’t have it at home but at the previous job we had a brooch set to cut a keyway in any hub, I could cut the keyway in the magnet to what I needed to retard the timing, it never occurred to me to do it.

Bad idea, it will delaminate. If you want to hock out your own keyway, its best to weld the keyway on the crank and recut it.

https://www.amazon.com/OIIKI-Internal-Starlock-Fasteners-Assortment/dp/B08ZCDDWNY/ref=asc_df_B08ZCDDWNY/?tag=hyprod-20&linkCode=df0&hvadid=507656698213&hvpos=&hvnetw=g&hvrand=3364385649625016654&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9024867&hvtargid=pla-1250080488412&psc=1

use this, or an external star washer, bend the tab in, slap a flat washer on top. add the nut, adjust where you want the magnet. Lock it all down. I use this method and it works perfect. Cost a few cents, and you have modified nothing. To go back to stock, take the washers off, slap the key back in. boom all factory again.

 

[Greg58]

I think cannonball has filed the magnet on some that were not cut to specs, what I was referring to on the key was using a wider key and cut down the Bottom half on one side and top half on the other. I’ve made a few when mcgivering a piece of machinery back together to make it till parts came in.