Surging at High Speeds

[Midwestscoot]

I picked up a my first Genuine scooter this weekend...a 2009 Blackjack and so far I'm loving it! Whats the top speed on these? It has 4,500 miles on it and seems to run great until I hit 65mph indicated speed. Once I hit 65mph on the speedometer the engine almost doesn't want to go faster and feels like it starts to surge if I keep accelerating. It backfired once after I started gaining a little speed downhill and broke 65, so I've been keeping it under 65 since. Do I have an issue? Or is this normal?

[Christophers]

I picked up a my first Genuine scooter this weekend...a 2009 Blackjack and so far I'm loving it! Whats the top speed on these? It has 4,500 miles on it and seems to run great until I hit 65mph indicated speed. Once I hit 65mph on the speedometer the engine almost doesn't want to go faster and feels like it starts to surge if I keep accelerating. It backfired once after I started gaining a little speed downhill and broke 65, so I've been keeping it under 65 since. Do I have an issue? Or is this normal?

I routinely peg my speedometer on a good downhill run.

Your flat top speed will depend on your size and riding style (tucked vs. sitting straight up). Not sure what the surging is.

The "backfiring" that you experienced sounds like it might be lean popping. These bikes are already jetted pretty lean and when you are off the throttle going downhill at speed in top gear you can get a pretty lean combustion.

[GregsBuddy]

My 170i does the same thing under certain conditions running open or nearly open throttle at or near top speed. It is the rev limiter cutting in.
The popping is from unburned charge being lit off in the muffler.

[Midwestscoot]

My 170i does the same thing under certain conditions running open or nearly open throttle at or near top speed. It is the rev limiter cutting in.
The popping is from unburned charge being lit off in the muffler.

That makes sense. I didn't know if it had a rev limiter or not. Thanks!

[GregsBuddy]

I verified the rev limiter was present last week. After returning from a long ride where I experienced the "surge" I held the throttle open far enough to run up against the limiter. The engine turned on/off/on/off and stopped from overreving. Without a tachometer, I don't know what RPM this happened. No damage to the engine, of course, that's what the rev limiter is for!

[JettaKnight]

Am I right that it's not a surge, but a cut or loss?

[GregsBuddy]

It's likely the problem...

[Midwestscoot]

I ended up removing all the panels to repaint the scooter and I noticed a crack in the air intake hose. I sealed it up and it no longer has the surge at high speeds. I think it was drawing in extra air and running lean. It will now top out between 70-75mph indicated speed and seems to run much better.

[GregsBuddy]

That will do it!
70-75? That's spinning!

[k1dude]

70-75 indicated?

Either your speedo is very ambitious, or the nitro bottle you installed is working.

[GregsBuddy]

I know my 170i won't get to this speed on the flats and/or downhill runs I've ridden. But, I'm open minded!

[Christophers]

70-75 indicated?

Either your speedo is very ambitious, or the nitro bottle you installed is working.

These scoots will run that fast - even with a stock CDI.
As I noted above, I routinely peg the speedo on my Buddy on downhill runs.
(I prefer to back it off to ~ 70 indicated just for comfort on 10" wheels).

Also as indicated, the Buddy 125s/150s DO NOT have a CDI rev limiter. I don't know what the case is with the 170i/fuel injected bikes. Your 170i may indeed have a rev limiter.

Note that although the aftermarket CDIs are sold as not having a rev limiter this does not mean that the OEM CDI does. It does not. I have seen no difference in top end rev limits between stock and NCY CDIs. (I was also chasing top end stuttering - which also ended up being an intake air leak.)

I do have tachometer on my scooter.

[GregsBuddy]

How high do 170i's spin? I've never had an accurate tach on my scoot'.

[k1dude]

70-75 indicated?

Either your speedo is very ambitious, or the nitro bottle you installed is working.

These scoots will run that fast - even with a stock CDI.
As I noted above, I routinely peg the speedo on my Buddy on downhill runs.
(I prefer to back it off to ~ 70 indicated just for comfort on 10" wheels).

Also as indicated, the Buddy 125s/150s DO NOT have a CDI rev limiter. I don't know what the case is with the 170i/fuel injected bikes. Your 170i may indeed have a rev limiter.

Note that although the aftermarket CDIs are sold as not having a rev limiter this does not mean that the OEM CDI does. It does not. I have seen no difference in top end rev limits between stock and NCY CDIs. (I was also chasing top end stuttering - which also ended up being an intake air leak.)

I do have tachometer on my scooter.

I've hit 73 indicated on my 125, but only on a pretty good downhill. Midwestscoot is posting from Nebraska, so I imagine his 70 - 75 indicated is on the flat - which is impressive to say the least. I don't think I've ever heard of a stock Buddy hitting those speeds on the flat before.

[Christophers]

How high do 170i's spin? I've never had an accurate tach on my scoot'.

I actually can't even tell you that information for a 125.
I installed a tach that only reads up to 9000. The engine will peg the tachometer - but again - something I am very conscious to avoid doing.
I never thought I would need readings above 9000, and I should probably never be running the engine that fast.

[Point37]

How high do 170i's spin? I've never had an accurate tach on my scoot'.

I actually can't even tell you that information for a 125.
I installed a tach that only reads up to 9000. The engine will peg the tachometer - but again - something I am very conscious to avoid doing.
I never thought I would need readings above 9000, and I should probably never be running the engine that fast.

nice mirrors!..that's not your key code tag hanging on your key chain is it?

[Midwestscoot]

70-75 indicated?

Either your speedo is very ambitious, or the nitro bottle you installed is working.

These scoots will run that fast - even with a stock CDI.
As I noted above, I routinely peg the speedo on my Buddy on downhill runs.
(I prefer to back it off to ~ 70 indicated just for comfort on 10" wheels).

Also as indicated, the Buddy 125s/150s DO NOT have a CDI rev limiter. I don't know what the case is with the 170i/fuel injected bikes. Your 170i may indeed have a rev limiter.

Note that although the aftermarket CDIs are sold as not having a rev limiter this does not mean that the OEM CDI does. It does not. I have seen no difference in top end rev limits between stock and NCY CDIs. (I was also chasing top end stuttering - which also ended up being an intake air leak.)

I do have tachometer on my scooter.

I've hit 73 indicated on my 125, but only on a pretty good downhill. Midwestscoot is posting from Nebraska, so I imagine his 70 - 75 indicated is on the flat - which is impressive to say the least. I don't think I've ever heard of a stock Buddy hitting those speeds on the flat before.

Yes, it is pretty flat here. I have no idea if the PO modded anything on this scooter, but it is a 150 and has the Prima exhaust as well. I'm sure that makes a small difference in top end. I also have a Vino 125 and my Buddy is a LOT faster.

[Midwestscoot]

How high do 170i's spin? I've never had an accurate tach on my scoot'.

I actually can't even tell you that information for a 125.
I installed a tach that only reads up to 9000. The engine will peg the tachometer - but again - something I am very conscious to avoid doing.
I never thought I would need readings above 9000, and I should probably never be running the engine that fast.

Which bar end mirrors are you running. I like those!

[Point37]

How high do 170i's spin? I've never had an accurate tach on my scoot'.

I actually can't even tell you that information for a 125.
I installed a tach that only reads up to 9000. The engine will peg the tachometer - but again - something I am very conscious to avoid doing.
I never thought I would need readings above 9000, and I should probably never be running the engine that fast.

Which bar end mirrors are you running. I like those!

looks like the rizoma spy r...legit nice mirrors...crg and joker machine also make nice mirrors...
https://www.amazon.com/Rizoma-Mirror-Mo ... rizoma+spy

http://www.rizoma.com/universal/mirrors ... 5-bs294/en

...you can buy cheaper knock offs...these ctg mirrors...but i don't think the quality will be the same
https://www.amazon.com/CTG-Mirrors-DUCA ... p_89%3ACTG


i wonder how bicycle mirrors would work as far as vibrations go...

https://www.amazon.com/Mirrycle-MTB-Mou ... 2661618011

https://www.amazon.com/Hafny-Mirror-Sta ... 2661618011

[GregsBuddy]

Thanks, Christophers! That's interesting information. Above 9k! That's blazing along pretty well and these engines seem very happy at that RPM. Like your mod's.