Mods and top speed input request

o2jmpr · 08-02-2018, 03:41 PM

I would like you guys opinions on whether or not this combo of mods matches a top speed on the flats of ~58mph indicated at WOT.

I'm 280lbs.
800 indicated miles.
17front/50 rear gears
Stock chain
Stock carb with 110 main, 1 washer under needle and mixture tuned as best I could for highest rpm at idle.
Dr8EIX plug gapped to ~.35 or .36.

Bike starts, runs and idles well with this combo. I pulled the plug after normal riding a week ago and the center looked really good to me but was solid black at the end of the threads that led up about 4 threads (not oily, just black).
After I saw that I removed one of the two washers I had under the needle to lean it out a bit and that also eliminated a bit of deceleration/roll off popping I was getting.

I'm probably asking too much being 280lbs but I would like to be able to run 55mph actual under normal conditions without regearing and losing my low end pull. 58 indicated is probably really closer to 50 actual. Throw in a hill and it's more like 45 and I will get mowed down by traffic running that speed around where I live. I always try to stick to 45mph and under roads that's often not an option.

ChrisWNY · 08-02-2018, 03:48 PM

Why not drop down a few teeth on the rear sprocket...go with a 45T or 43T for the higher top end speed. You'll lose a little bit of power in the low end but it's not substantial. Ideally you want your spark plug to be a light tan or gray color. It's normal to see some black on the threads. You want to pay the most attention to the color of the electrode.

o2jmpr · 08-02-2018, 03:54 PM

Hmmm . Now I wonder if I’m not too lean. I’m torn because I know it’s better to be rich than lean but like I mentioned the deceleration roll off popping stopped after I pulled a washer which I assumed to be caused from extra fuel getting detonated by the hot cat. Ugghh. So many variables!
I had every intention of going to a 45 rear when I bought the bike but I LOVE It’s tractor like pull on the low end. If you say it’s not too much of a difference I suppose it’s worth it.

**JerryHawk250** · 08-02-2018, 04:05 PM

Are you still running the stock exhaust? Gutting the cat or installing a free flowing exhaust will help a good bit. I also agree on putting a smaller sprocket on the rear for better top end.

o2jmpr · 08-02-2018, 04:10 PM

Yup I’m stock exhaust. Removing the cat is beyond my scope of work and I’m a cheap ass Chinarider who doesn’t want to pay so much for an aftermarket.

I know I want my cake and eat it too. Ha.

o2jmpr · 08-02-2018, 05:18 PM

Tomorrow I’m gonna go back to two washers on the needle for safety and try to retune my mixture setting despite the cursing and burns from trying to get to that damn screw. I’ll bet my popping was more from the mixture setting than the jet needle. Seems like I had a little better top end before I tinkered and thought I was running rich. There is definitely an art to carb tuning that I haven’t quite figured out yet. I’d just feel better knowing I may be rich than lean

Maybe I’ll just ride 40 mph all the way to Megadans house on gravel roads and let him perform some voodoo on it.

ChipToothy · 08-02-2018, 05:19 PM

Quote:

Originally Posted by o2jmpr

Yup I’m stock exhaust. Removing the cat is beyond my scope of work and I’m a cheap ass Chinarider who doesn’t want to pay so much for an aftermarket.

I know I want my cake and eat it too. Ha.

Same boat as me. The cheap one.

Azhule · 08-02-2018, 06:11 PM

Quote:

Originally Posted by o2jmpr

Maybe I’ll just ride 40 mph all the way to Megadans house on gravel roads and let him perform some voodoo on it.

If he isn't home/available, I have also been known to perform a few Black Magic/Voodoo Rituals to help the top speed of a China Bike

o2jmpr · 08-02-2018, 06:25 PM

I’m from Des Moines. My butt would never make it to your neck of the woods without a trailer. ��. That said, I’m planning to head that direction next summer to do a bucket list ride of the alpine loop and a few famous passes.

o2jmpr · 08-02-2018, 06:59 PM

Back on topic. I just ordered the 45T rear. I trust you guys and whether I like it or not, I’m gonna have to sacrifice some torque for speed. I’ll report back in a few days with my new findings. I appreciate you all!

Digger · 08-02-2018, 07:26 PM

My setup on the carb is 2, .020 washers from a Mikuni needle fine adjustent kit.

ChrisWNY · 08-03-2018, 12:04 AM

My spark plug was spotless clean with a white electrode before I went up to a #120 main jet and dropped down a slot on the Mikuni jet needle (it's set in the middle from the factory, I went down one notch to richen the mixture). I did install the aftermarket exhaust which really opened up airflow through the engine, so I tuned the carb to run much richer through all the throttle settings. Even on the #110 main jet and the stock exhaust, that engine was still running lean.

Now my spark plug is dark, almost black, but not too dirty. It's definitely running on the rich side which is where I wanted it, the Hawk has a lot more power through all the gears. It uses more gas though...I'm probably getting 50mpg vs 60mpg. Worth it for the extra power and cooler engine temp.

The 45T rear sprocket will definitely add several mph, it will have noticeable improvement on the top end.

o2jmpr · 08-03-2018, 02:11 PM

Thanks for the replies. Digger posting his washer measurements got me to do the same. The washers I had in there were both .032 thick. Since Digger said he was running .040 total I just left mine at 1 washer. That’s awfully close.

I fiddled with my mixture again and just settled for 2 turns out. I honestly can’t tell an rpm difference at idle between 1/4 turn out and 4 turns out which on my bike are the points where the rpm noticeably drops just before dying.

Sprocket comes tomorrow. I’ll try the 17/45 combo first and if I absolutely hate it (some people around here have already expressed their disgust for this combo) I’ll go back to my 15T in the front and test it.

More to follow.

Sochin · 08-03-2018, 05:51 PM

I can go 65 indicated on my signature setup......and stock albeit modified exhaust....yeh.....cuz I'm cheee..eee..eeeeap

Digger · 08-03-2018, 08:54 PM

1st off I want to correct a previous post.
I stated I used 2, .020 shims on the needle for a total of .040, that was wrong. What I actually used was 2, .030 shims for a total of .060
Sorry if I caused any confusion.
As long as I was measuring things I thought I would measure how much on a 32mm VM Mikuni needle how one step of the needle clip is... .020
I also measured a Mikuni 30 pilot jet... .019
From memory, (which seems to be fading every day) people have posted using a 20 or 25 pilot jet on a Mikuni carb. Hope this helps the cheap folks out there

08-02-2018, 03:48 PM	#2
ChrisWNY Join Date: Jul 2018 Posts: 212	Why not drop down a few teeth on the rear sprocket...go with a 45T or 43T for the higher top end speed. You'll lose a little bit of power in the low end but it's not substantial. Ideally you want your spark plug to be a light tan or gray color. It's normal to see some black on the threads. You want to pay the most attention to the color of the electrode. __________________ 2018 RPS Hawk 250cc Mods so far: 1. Mikuni VM26 Carburetor w/#115 main jet 2. 17T/45T JT sprockets 3. JT 428 X-ring chain 4. Air box mod 5. Hawk Digital Cluster 6. Aftermarket IMS shift lever 7. Performance Aftermarket Exhaust 8. 295mm Nitrogen Gas Monoshock, 20W oil front forks
	0

08-02-2018, 04:05 PM	#4
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,553	Are you still running the stock exhaust? Gutting the cat or installing a free flowing exhaust will help a good bit. I also agree on putting a smaller sprocket on the rear for better top end. __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
	1

08-03-2018, 02:11 PM	#13
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	Thanks for the replies. Digger posting his washer measurements got me to do the same. The washers I had in there were both .032 thick. Since Digger said he was running .040 total I just left mine at 1 washer. That’s awfully close. I fiddled with my mixture again and just settled for 2 turns out. I honestly can’t tell an rpm difference at idle between 1/4 turn out and 4 turns out which on my bike are the points where the rpm noticeably drops just before dying. Sprocket comes tomorrow. I’ll try the 17/45 combo first and if I absolutely hate it (some people around here have already expressed their disgust for this combo) I’ll go back to my 15T in the front and test it. More to follow. Last edited by o2jmpr; 08-03-2018 at 02:12 PM. Reason: Spelling
	0

08-03-2018, 05:51 PM	#14
Sochin Join Date: Jul 2017 Location: Montucky Posts: 209	I can go 65 indicated on my signature setup......and stock albeit modified exhaust....yeh.....cuz I'm cheee..eee..eeeeap __________________ 1991 Kawasaki KLR250
	0

08-02-2018, 03:41 PM	#1
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	Mods and top speed input request I would like you guys opinions on whether or not this combo of mods matches a top speed on the flats of ~58mph indicated at WOT. I'm 280lbs. 800 indicated miles. 17front/50 rear gears Stock chain Stock carb with 110 main, 1 washer under needle and mixture tuned as best I could for highest rpm at idle. Dr8EIX plug gapped to ~.35 or .36. Bike starts, runs and idles well with this combo. I pulled the plug after normal riding a week ago and the center looked really good to me but was solid black at the end of the threads that led up about 4 threads (not oily, just black). After I saw that I removed one of the two washers I had under the needle to lean it out a bit and that also eliminated a bit of deceleration/roll off popping I was getting. I'm probably asking too much being 280lbs but I would like to be able to run 55mph actual under normal conditions without regearing and losing my low end pull. 58 indicated is probably really closer to 50 actual. Throw in a hill and it's more like 45 and I will get mowed down by traffic running that speed around where I live. I always try to stick to 45mph and under roads that's often not an option.
	0

08-02-2018, 03:54 PM	#3
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	Hmmm . Now I wonder if I’m not too lean. I’m torn because I know it’s better to be rich than lean but like I mentioned the deceleration roll off popping stopped after I pulled a washer which I assumed to be caused from extra fuel getting detonated by the hot cat. Ugghh. So many variables! I had every intention of going to a 45 rear when I bought the bike but I LOVE It’s tractor like pull on the low end. If you say it’s not too much of a difference I suppose it’s worth it.
	0

08-02-2018, 04:10 PM	#5
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	Yup I’m stock exhaust. Removing the cat is beyond my scope of work and I’m a cheap ass Chinarider who doesn’t want to pay so much for an aftermarket. I know I want my cake and eat it too. Ha.
	3

08-02-2018, 05:18 PM	#6
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	Tomorrow I’m gonna go back to two washers on the needle for safety and try to retune my mixture setting despite the cursing and burns from trying to get to that damn screw. I’ll bet my popping was more from the mixture setting than the jet needle. Seems like I had a little better top end before I tinkered and thought I was running rich. There is definitely an art to carb tuning that I haven’t quite figured out yet. I’d just feel better knowing I may be rich than lean Maybe I’ll just ride 40 mph all the way to Megadans house on gravel roads and let him perform some voodoo on it.
	0

08-02-2018, 06:25 PM	#9
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	I’m from Des Moines. My butt would never make it to your neck of the woods without a trailer. ��. That said, I’m planning to head that direction next summer to do a bucket list ride of the alpine loop and a few famous passes.
	1

08-02-2018, 06:59 PM	#10
o2jmpr Join Date: May 2017 Location: Des Moines, IA Posts: 120	Back on topic. I just ordered the 45T rear. I trust you guys and whether I like it or not, I’m gonna have to sacrifice some torque for speed. I’ll report back in a few days with my new findings. I appreciate you all!
	1

08-02-2018, 07:26 PM	#11
Digger Join Date: Jul 2018 Posts: 64	My setup on the carb is 2, .020 washers from a Mikuni needle fine adjustent kit.
	0

08-03-2018, 12:04 AM	#12
ChrisWNY Join Date: Jul 2018 Posts: 212	My spark plug was spotless clean with a white electrode before I went up to a #120 main jet and dropped down a slot on the Mikuni jet needle (it's set in the middle from the factory, I went down one notch to richen the mixture). I did install the aftermarket exhaust which really opened up airflow through the engine, so I tuned the carb to run much richer through all the throttle settings. Even on the #110 main jet and the stock exhaust, that engine was still running lean. Now my spark plug is dark, almost black, but not too dirty. It's definitely running on the rich side which is where I wanted it, the Hawk has a lot more power through all the gears. It uses more gas though...I'm probably getting 50mpg vs 60mpg. Worth it for the extra power and cooler engine temp. The 45T rear sprocket will definitely add several mph, it will have noticeable improvement on the top end. __________________ 2018 RPS Hawk 250cc Mods so far: 1. Mikuni VM26 Carburetor w/#115 main jet 2. 17T/45T JT sprockets 3. JT 428 X-ring chain 4. Air box mod 5. Hawk Digital Cluster 6. Aftermarket IMS shift lever 7. Performance Aftermarket Exhaust 8. 295mm Nitrogen Gas Monoshock, 20W oil front forks
	0

08-03-2018, 08:54 PM	#15
Digger Join Date: Jul 2018 Posts: 64	1st off I want to correct a previous post. I stated I used 2, .020 shims on the needle for a total of .040, that was wrong. What I actually used was 2, .030 shims for a total of .060 Sorry if I caused any confusion. As long as I was measuring things I thought I would measure how much on a 32mm VM Mikuni needle how one step of the needle clip is... .020 I also measured a Mikuni 30 pilot jet... .019 From memory, (which seems to be fading every day) people have posted using a 20 or 25 pilot jet on a Mikuni carb. Hope this helps the cheap folks out there
	0