More mysterious rpm issues.

CaptainKP · 06-29-2020, 10:37 AM

Around 100 miles on the Hawk now and have re-jetted the carb to recommended specs & adjusted the valves before I road it.

It has a little popping when letting off the throttle. But even more annoying is that sometimes after it warms up the idle drops and it stalls out. If I keep idle set at 2k it doesn't happen but when I have it adjusted for 1.5-1.6k it happens every time eventually.

I checked for a vacuum leak with some carb cleaner around the obvious places and didn't notice any difference in rpms.

Any ideas?

mtiberio · 06-29-2020, 11:07 AM

Adjust valves again

CaptainKP · 06-29-2020, 02:49 PM

Thanks!

How frequently are people adjusting their valve lash during the break in period? I'll try adjusting them tonight and see if that helps.

TestYourMight · 06-29-2020, 05:24 PM

I had quite a bit of difficulty finding TDC. At first, I couldn't figure out if I was on the compression or the exhaust stroke. I think the best piece of advice I found was that the valves will be tighter on the exhaust stroke. Disregard this reply in the highly likely scenario that you are not as mechanically inept as me.

CaptainKP · 06-29-2020, 09:51 PM

I adjusted them tonight & they were very loose. And it sounds much better (it was getting pretty loud after 100 miles & an original valve adjustment)

I can't tell for sure until I take it for an hour+ or so ride but that might have been the problem. These engines are solid but old school & I forget it requires constant tinkering.

Unfortunately, I'm now running into chain rubbing into the tire issues. I have a new chain and two sprockets coming this weekend and I'll try to figure out a good way to realign the chain guide rail that is way out of wack.

CaptainKP · 07-11-2020, 07:53 PM

Well, I just can't get this sorted out. Adjusted the valves & thought it was running better. But took it for a ride today and after it warmed up if I had idle set at 1.5k - 1.6k it would eventually just falling and then die. If I set it at 2k it stays running but fluctuates every couple minutes. Sometimes it revs up sometimes it revs down. I can keep it set at 1.5 - 1.6 but when I hit stoplights I have to give it a little gas to stay alive.

When its a cold start it idles fine.

Any ideas of what I can check?

Wild Dog · 07-11-2020, 08:46 PM

Quote:

Originally Posted by CaptainKP

Well, I just can't get this sorted out. Adjusted the valves & thought it was running better. But took it for a ride today and after it warmed up if I had idle set at 1.5k - 1.6k it would eventually just falling and then die. If I set it at 2k it stays running but fluctuates every couple minutes. Sometimes it revs up sometimes it revs down. I can keep it set at 1.5 - 1.6 but when I hit stoplights I have to give it a little gas to stay alive.

When its a cold start it idles fine.

Any ideas of what I can check?

You are rich.

Goob · 07-12-2020, 12:17 PM

Quote:

Originally Posted by CaptainKP

Well, I just can't get this sorted out. Adjusted the valves & thought it was running better. But took it for a ride today and after it warmed up if I had idle set at 1.5k - 1.6k it would eventually just falling and then die. If I set it at 2k it stays running but fluctuates every couple minutes. Sometimes it revs up sometimes it revs down. I can keep it set at 1.5 - 1.6 but when I hit stoplights I have to give it a little gas to stay alive.

When its a cold start it idles fine.

Any ideas of what I can check?

I agree with Wild Dog. You likely need a leaner PILOT jet. Mine was doing EXACTLY the same thing as your description, even after a valve adjustment, until I changed it out.

If your jet is on the intake side of the carb, this means a larger jet (as it regulates air). If your jet is on the exhaust side, this means a smaller jet (as it regulates fuel).

When you change it out put the Pilot jet screw at 1.5 turns out as a starting point, ride around a bit to get it warmed up, then adjust he Pilot screw up or down to get the idle speed you want; tweaking the idle screw along the way. If it is still doing the same thing, then go another size leaner and repeat.

CaptainKP · 07-12-2020, 03:58 PM

Thanks guys. I ordered a 27.5 and a 25 pilot initially. I'll throw in the 25 and see how it goes. I'm already at 1.5 turns on mixture.

BuffaloChinaRider · 07-16-2020, 09:11 AM

Quote:

Originally Posted by CaptainKP

Thanks guys. I ordered a 27.5 and a 25 pilot initially. I'll throw in the 25 and see how it goes. I'm already at 1.5 turns on mixture.

Where did you order those smaller pilot jets from? I'm having trouble finding them for my keihin carb. Only see 32 and bigger slow jets. I have the same issue as you and I have changed out/adjusted everything else.

Kenstogie · 07-16-2020, 09:55 AM

Quote:

Originally Posted by BuffaloChinaRider

Where did you order those smaller pilot jets from? I'm having trouble finding them for my keihin carb. Only see 32 and bigger slow jets. I have the same issue as you and I have changed out/adjusted everything else.

probably jetsrus..... thats my guess

BuffaloChinaRider · 07-16-2020, 10:58 AM

Quote:

Originally Posted by Kenstogie

probably jetsrus..... thats my guess

Just checked they don't have the size #25 for my pilot jet. They have #35 and up. I just didn't want to buy the #25 on ebay for $14 but I might have to suck it up lol

**JerryHawk250** · 07-16-2020, 11:06 AM

Quote:

Originally Posted by BuffaloChinaRider

Just checked they don't have the size #25 for my pilot jet. They have #35 and up. I just didn't want to buy the #25 on ebay for $14 but I might have to suck it up lol

The smallest i found was a 28 but it came on the slow boat. https://www.ebay.com/itm/Carb-Slow-P...72.m2749.l2649

BuffaloChinaRider · 07-16-2020, 01:32 PM

Quote:

Originally Posted by JerryHawk250

The smallest i found was a 28 but it came on the slow boat. https://www.ebay.com/itm/Carb-Slow-P...72.m2749.l2649

Thanks jerry! I'm gonna order that #28 , I just like having extra. Right now the pilot is not stamped BUT I bought a similar carb than came with a #42 pilot and that's way too rich for my aftermarket exhaust. My plugs are fouling up right off of idle and a few revs .also still idling funny going up and down. I have a #32 with me so I'm gonna swap that possible #42 that came stock in my carb to the #32 and see what difference it makes.

Kenstogie · 07-16-2020, 04:53 PM

maybe these...l??
https://www.amazon.com/TC-Motor-Carb.../dp/B07QXNNM5V

06-29-2020, 10:37 AM	#1
CaptainKP Join Date: Apr 2020 Location: Atlanta, GA Posts: 58	More mysterious rpm issues. Around 100 miles on the Hawk now and have re-jetted the carb to recommended specs & adjusted the valves before I road it. It has a little popping when letting off the throttle. But even more annoying is that sometimes after it warms up the idle drops and it stalls out. If I keep idle set at 2k it doesn't happen but when I have it adjusted for 1.5-1.6k it happens every time eventually. I checked for a vacuum leak with some carb cleaner around the obvious places and didn't notice any difference in rpms. Any ideas?
	0

07-16-2020, 04:53 PM	#15
Kenstogie Join Date: Apr 2019 Posts: 336	maybe these...l?? https://www.amazon.com/TC-Motor-Carb.../dp/B07QXNNM5V __________________ been around bikes for a while.... honda 72 cb200t, zuki 96?/2002 katana, 12 vstrom,09 vstar, kawi ltd440, 82 zuki Gs1100, Tao Tbr7 all about the Tao MotorsTBR7 http://www.chinariders.net/showthread.php?t=25553
	0

06-29-2020, 11:07 AM	#2
mtiberio Join Date: Jun 2016 Location: Arlington, VA Posts: 258	Adjust valves again __________________ 4 time WERA SuperVintage Roadracing National Champion, SCTA Land Speed Record Holder, 3rd AMA Motorcycle GP of Miami
	0

06-29-2020, 02:49 PM	#3
CaptainKP Join Date: Apr 2020 Location: Atlanta, GA Posts: 58	Thanks! How frequently are people adjusting their valve lash during the break in period? I'll try adjusting them tonight and see if that helps.
	0

06-29-2020, 05:24 PM	#4
TestYourMight Join Date: May 2020 Posts: 20	I had quite a bit of difficulty finding TDC. At first, I couldn't figure out if I was on the compression or the exhaust stroke. I think the best piece of advice I found was that the valves will be tighter on the exhaust stroke. Disregard this reply in the highly likely scenario that you are not as mechanically inept as me.
	1

06-29-2020, 09:51 PM	#5
CaptainKP Join Date: Apr 2020 Location: Atlanta, GA Posts: 58	I adjusted them tonight & they were very loose. And it sounds much better (it was getting pretty loud after 100 miles & an original valve adjustment) I can't tell for sure until I take it for an hour+ or so ride but that might have been the problem. These engines are solid but old school & I forget it requires constant tinkering. Unfortunately, I'm now running into chain rubbing into the tire issues. I have a new chain and two sprockets coming this weekend and I'll try to figure out a good way to realign the chain guide rail that is way out of wack.
	0

07-11-2020, 07:53 PM	#6
CaptainKP Join Date: Apr 2020 Location: Atlanta, GA Posts: 58	Well, I just can't get this sorted out. Adjusted the valves & thought it was running better. But took it for a ride today and after it warmed up if I had idle set at 1.5k - 1.6k it would eventually just falling and then die. If I set it at 2k it stays running but fluctuates every couple minutes. Sometimes it revs up sometimes it revs down. I can keep it set at 1.5 - 1.6 but when I hit stoplights I have to give it a little gas to stay alive. When its a cold start it idles fine. Any ideas of what I can check?
	0

07-12-2020, 03:58 PM	#9
CaptainKP Join Date: Apr 2020 Location: Atlanta, GA Posts: 58	Thanks guys. I ordered a 27.5 and a 25 pilot initially. I'll throw in the 25 and see how it goes. I'm already at 1.5 turns on mixture.
	0