No Power 5th Gear
 

New RPS Hawk 250; but lacks power at top end. I've been reading 60 mph top stock, but I couldn't get it above 42. I rejetted the stock carb to 115, opened air box a bit, set the mixture at 1.5 turns out, set valve lash to .002, and was able to get top to 45-46 on flat ground. I thought it may be speedometer, but GPS confirms my speed at ~46.

Two sprockets arrived today and it feels good in lower gears, but I can't get any speed out of 5th gear... bogs out. My goal is a pretty simple 60-65 top speed highway, 55 cruising. Based on everything I've read, I should be there, but it's struggling. Any ideas?

I'm in Georgia, at sea level, temp ~70.

Are you still running stock exhaust? If so a 115 may be too rich. Is it bogging or cutting out on top end? If cutting out then it's too rich. To run a 115 jet you will need to remove the cat or go with a after market header pipe.

A 115 main is too big without the cat removed or a different exhaust. Try a 110. Also, make sure your choke is not in the half position. That can do it too.

I'd consider it more bogging out, I get almost nothing out of 5th gear, and it will intermittently sputter if I hold full throttle.

I'll switch jet out to 110 tomorrow to give it a try, and recheck valves, maybe up those to .003/.004. Unfortunately, even before rejetting stock carb from 98, I had this same behavior, but maybe I've gone to the two opposite ends of spectrum.

I did confirm choke was open (took air intake off back of carb). With the air intake completely off, topping at 49. This is my first bike, is it normal for a battery to require charging every few days? I've got ~75 miles on it so far.

Appreciate the input; this has been driving me nuts for a few days!

The stock battery is pretty mediocre in terms of quality. Almost all of us have swapped it out for a better one.

Something else worth noting. The stock spark plug is cheap and crappy, change it out. Also, check the ground points to the chassis. A poor ground can cause all sorts of issues, including weak spark or ignition. Ground wires are standard Honda green.

Definitely sounds rich. Like Megadan stated . Change out the crappy plug that comes with it to a NGK.

I just put on the mikuni. I am stock at sea level. I am running a 110 and a 25. Runs like a champ. 60 is about all it will do but it runs great.

[forgot to mention] I am running the NGK Iridium.

The spark plug looked decent when I pulled it, although more brown than grey... I can't wait for 4pm so I can get home and recheck valve lash and flip in the 110 jet though. I also purchased the $99 exhaust system just in case it's something to do with exhaust.

This is likely a silly question, but where does the ground attach to chassis? I pulled fenders and headlight last night and nothing stuck out (almost every wire is green). Only thing left to pull is the fuel tank to to look under it.

:tup:

I do not know how many miles you have on your Hawk but these engines come very tight, for most people it seems it takes anywhere from 500 to 1000 miles to have it really broken in well and running to its full potential.

Even my hawk could reach 55mph within the first 200 miles. I was hitting over 60 by 500.

I am personally leaning toeard 2 conditions adding up. Too rich main jet and the ignition is weak and cutting out under heavy load, aka wot in a high gear.

Unfortunately, similar after rejetting to 110. I upped my intake/exhaust lash to .003". Stripped paint under the ground wire. I do have ~100 miles on it at this point. With the 17/45 setup, I'd think it would do 60 easy, even @100 miles break in.

Exhaust system is slated to be here Friday, but I'll be surprised if that completely opens up another 20 mph. Recorded my GPS speedometer just a few minutes ago with audio, maybe that'll help?

https://youtu.be/QtNTK_rvo8s

+spark plug pics post-ride.

https://photos.app.goo.gl/yqOQeEZBEkXrOH5B3

Its definitely not rapping all the way out, Does the throttle lose all pick up in the last 1/4 turn or is it wide open?

If its wide open then you might need to re-adjust your throttle cable because you never got high in RPM's in any gear.

If its falling on its face at the top of the throttle then you need to look further into your jetting etc..

That bike should sing wide open but its not getting there.

Re: Exhaust system is slated to be here Friday, but I'll be surprised if that completely opens up another 20 mph.


Unless yers is all faulted up and clogged to chit! that will make it bog.

Personally I found that gear setup too tall, probly fine on flat roads, but I got lots of hills and wind to fight against.

id rather be able to get the revs up to hold speed and go a bit slower. 45 is pitiful tho :hmm: