Carb question

Plukey · 02-27-2012, 05:58 PM

Hey,
Trying to tune a 30 mm mikuni carb on a zs200gy-a dual sport. I believe I have a 30 slow & 130 main.. I plan on taking it apart this weekend To be sure. It's starting up fine, but what I've noticed is when I reach about 60 mph at full throttle it jerks. Is this due to a small main jet? I live in Va it's about 52 degrees right now, they say it will be around 70 this weekend. I'm sure the weather may play a roll, but how much I wonder.

Thanks in advance!!!!

Plukey · 02-27-2012, 07:24 PM

Also.... Is what I'm describing a rev limiter? This is the first time I had it on the road, I've mostly just ride trails..never going that fast! I'm assuming the max top end speed is 55-60 on my 200.

Weldangrind · 02-27-2012, 10:24 PM

You might be hitting a rev limiter, but I doubt it. Confirming the jet size is a good step, as is cleaning the carb. It might also be time to set the valves.

BTW, if you're running the stock carb, it's more commonly a Keihin copy, not a Mikuni. Is your carb stock? Have you modified the exhaust or swapped the air filter for a free-flowing unit?

Plukey · 02-28-2012, 06:58 AM

The muffler is original, the only mods I've done is the carb & a UNI air filter & I purchaced a new odometer & headlamp. I bought it with a total 250 original miles on the engine. I bought the carb off EBay... I suppose it's a true Mikuni, I'm sure that's debaitable. What is the top speed on these bikes? I bought a few new plugs, how long should I run the bike before I check it to see if it's running lean or rich.

Weldangrind · 02-28-2012, 10:28 AM

If you bought a 30mm Mikuni on eBay for around $40 (including shipping), then it likely came with a 100 main and a 20 slow jet. Did you replace the jets when you received the carb? If not, My guess is that it's lean. If it indeed has a 130 main jet, I believe it's too rich.

You can check the air / fuel status with just one ride if you do a plug chop. One way is to warm up the engine, head for a secondary highway and ride at WOT in top gear. While at WOT and still holding the throttle open, hit the kill switch. The idea is to freeze the plug condition in time. Once the engine has cooled enough, pull the plug and please take some pics; it's good information for other members.

Expect to max out around 60mph on any 200cc air cooled bike.

Plukey · 02-28-2012, 01:45 PM

Your exactly right, it was around $40.00 & those were the sizes it came with. I replaced them with a 35 slow and 150 main...1st time. Way to rich!!! 2nd, I think i went down to a 30 slow & 130/135 main. I have 110 & 115 ready ...do u think that's more sutible? I will run the test you described and take some pic's this evening.
Thanks!

Plukey · 02-28-2012, 05:47 PM

http://s1079.photobucket.com/albums/...1330467983.jpg

I hope I did this right....the first two pic's are the old plug, this one has maybe 10 hrs of moderate trail riding. The next three is a brand new plug that u just put in drove on a secondary road reached 60 mph killed the engine. It's 49 degrees here.

Weldangrind · 02-29-2012, 01:10 AM

So, here's your old plug, which looks really rich:

And here's the new plug after a plug chop:

To me, the plug looks like it's in a rich environment. Perhaps some of our esteemed members will chime in. Bottom line is that if you're running a 130 main, it's too rich. I'd recommend a 110 main and 25 slow to start.

Brockway · 03-02-2012, 11:03 AM

I was thinking about doing this upgrade for my TMEC 200. This is the 30mm Mikuni carb everyone's talking about, right?

http://www.ebay.com/itm/MIKUNI-Carbu...#ht_3170wt_961

Want to buy the 110 main and 25 pilot jet, but I can't tell which jets are right. What is it, a CBMK30, a VM30?

Weldangrind · 03-02-2012, 11:20 AM

That's the carb I've purchased a few times now, and you found it on sale. Grab one!

I can't recall what the actual designation is, because I buy the jets over the counter at the local Yamaha dealer. The main jet is a very available large round head style. When you receive your carb, it will be easy to remove the jets and compare them with the pics on www.jetsrus.com . If you need specifics, let me know.

Frog · 03-02-2012, 02:37 PM

Quote:

Originally Posted by Brockway

I was thinking about doing this upgrade for my TMEC 200. This is the 30mm Mikuni carb everyone's talking about, right?

http://www.ebay.com/itm/MIKUNI-Carbu...#ht_3170wt_961

Want to buy the 110 main and 25 pilot jet, but I can't tell which jets are right. What is it, a CBMK30, a VM30?

That's the right carb but the wrong price in my view. I paid Â£21 for mine delivered - around $30

Frog

Frog · 03-02-2012, 02:43 PM

Hi Plukey

I have just installed the same carb and have exactly the same issue:-

Good starting, idling and mid throttle but major misfire at high revs (indicated 7k) - I am not sure if it is carb or rev limiter - although I have 'racing' CDI on and I think this should not be the case...

I too have standard exhaust on at present and uni filter

Be sure to post if you crack it and I will do the same.

Frog

Brockway · 03-02-2012, 02:58 PM

Bought it. $35 shipped USPS priority is the cheapest I've seen, 21 pounds is about $33 at current exchange rates. Will be months before I can install it since I'm out of the country, but should be fun to mess with.

Frog · 03-02-2012, 03:05 PM

$35 is a good price

Definitely a better carb that the original - instant starting and rock solid slow tick over + more performance.

I Just need to sort my mis-fire / rev limit problem..

Frog

Plukey · 03-04-2012, 06:59 PM

Gentlemen,

Since my last post, I removed the carb & I had 32.5 slow & 135 main. As pictured above we can all agree it looked really rich..... I went down to 115 main & 25 slow as Weldangrind suggested. I had a little trouble starting the bike; it took a few extra turns than before to fire up, so I decided to go up on the slow to#30. Put it all back together & it fired up great mid throttle ran smooth, it maxed out at 60 mph no bucking or kicking. I didn't do a plug chop yet...but I think itâ€™s finally getting close! Iâ€™m happy with this adjustment.

Frog....I just bought Different Jets from www.Jetsru.com as Weldangrind suggested..Purchased slow jets from 20 - 40 increments of five, & 110 - 150 main. Alot of jet changeing.. carb on & off..... My bike feels & sounds like it maxes out at 60 mph; Iâ€™m not always going that fast cause I'm normally in the woods on trails. But 55 mph is smooth and it handles great at those speeds. i wouldnt expect anymore than that out of a 200cc bike... Please keep us posted on any break thru's you may have.

Weldangrind,
I keep reading that the weather makes a difference, Hot air Vs cold air when I did these changes it was around 40 degrees.. When it hits 70 & above in the upcoming months here in Virginia will it run richer? What are your thoughts?

02-27-2012, 05:58 PM	#1
Plukey Join Date: Nov 2011 Location: Poquoson Va Posts: 73	Carb question Hey, Trying to tune a 30 mm mikuni carb on a zs200gy-a dual sport. I believe I have a 30 slow & 130 main.. I plan on taking it apart this weekend To be sure. It's starting up fine, but what I've noticed is when I reach about 60 mph at full throttle it jerks. Is this due to a small main jet? I live in Va it's about 52 degrees right now, they say it will be around 70 this weekend. I'm sure the weather may play a roll, but how much I wonder. Thanks in advance!!!!
	0

02-28-2012, 10:28 AM	#5
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	If you bought a 30mm Mikuni on eBay for around $40 (including shipping), then it likely came with a 100 main and a 20 slow jet. Did you replace the jets when you received the carb? If not, My guess is that it's lean. If it indeed has a 130 main jet, I believe it's too rich. You can check the air / fuel status with just one ride if you do a plug chop. One way is to warm up the engine, head for a secondary highway and ride at WOT in top gear. While at WOT and still holding the throttle open, hit the kill switch. The idea is to freeze the plug condition in time. Once the engine has cooled enough, pull the plug and please take some pics; it's good information for other members. Expect to max out around 60mph on any 200cc air cooled bike. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

02-29-2012, 01:10 AM	#8
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	So, here's your old plug, which looks really rich: And here's the new plug after a plug chop: To me, the plug looks like it's in a rich environment. Perhaps some of our esteemed members will chime in. Bottom line is that if you're running a 130 main, it's too rich. I'd recommend a 110 main and 25 slow to start. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

03-02-2012, 11:20 AM	#10
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	That's the carb I've purchased a few times now, and you found it on sale. Grab one! I can't recall what the actual designation is, because I buy the jets over the counter at the local Yamaha dealer. The main jet is a very available large round head style. When you receive your carb, it will be easy to remove the jets and compare them with the pics on www.jetsrus.com . If you need specifics, let me know. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

02-27-2012, 07:24 PM	#2
Plukey Join Date: Nov 2011 Location: Poquoson Va Posts: 73	Also.... Is what I'm describing a rev limiter? This is the first time I had it on the road, I've mostly just ride trails..never going that fast! I'm assuming the max top end speed is 55-60 on my 200.
	0

02-27-2012, 10:24 PM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	You might be hitting a rev limiter, but I doubt it. Confirming the jet size is a good step, as is cleaning the carb. It might also be time to set the valves. BTW, if you're running the stock carb, it's more commonly a Keihin copy, not a Mikuni. Is your carb stock? Have you modified the exhaust or swapped the air filter for a free-flowing unit? __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
	0

02-28-2012, 06:58 AM	#4
Plukey Join Date: Nov 2011 Location: Poquoson Va Posts: 73	The muffler is original, the only mods I've done is the carb & a UNI air filter & I purchaced a new odometer & headlamp. I bought it with a total 250 original miles on the engine. I bought the carb off EBay... I suppose it's a true Mikuni, I'm sure that's debaitable. What is the top speed on these bikes? I bought a few new plugs, how long should I run the bike before I check it to see if it's running lean or rich.
	0

02-28-2012, 01:45 PM	#6
Plukey Join Date: Nov 2011 Location: Poquoson Va Posts: 73	Your exactly right, it was around $40.00 & those were the sizes it came with. I replaced them with a 35 slow and 150 main...1st time. Way to rich!!! 2nd, I think i went down to a 30 slow & 130/135 main. I have 110 & 115 ready ...do u think that's more sutible? I will run the test you described and take some pic's this evening. Thanks!
	0

02-28-2012, 05:47 PM	#7
Plukey Join Date: Nov 2011 Location: Poquoson Va Posts: 73	http://s1079.photobucket.com/albums/...1330467983.jpg I hope I did this right....the first two pic's are the old plug, this one has maybe 10 hrs of moderate trail riding. The next three is a brand new plug that u just put in drove on a secondary road reached 60 mph killed the engine. It's 49 degrees here.
	0

03-02-2012, 11:03 AM	#9
Brockway Join Date: Nov 2011 Location: Sicily, but from Texas Posts: 56	I was thinking about doing this upgrade for my TMEC 200. This is the 30mm Mikuni carb everyone's talking about, right? http://www.ebay.com/itm/MIKUNI-Carbu...#ht_3170wt_961 Want to buy the 110 main and 25 pilot jet, but I can't tell which jets are right. What is it, a CBMK30, a VM30?
	0

03-02-2012, 02:43 PM	#12
Frog Join Date: May 2008 Location: Hampshire England Posts: 191	Hi Plukey I have just installed the same carb and have exactly the same issue:- Good starting, idling and mid throttle but major misfire at high revs (indicated 7k) - I am not sure if it is carb or rev limiter - although I have 'racing' CDI on and I think this should not be the case... I too have standard exhaust on at present and uni filter Be sure to post if you crack it and I will do the same. Frog
	0

03-02-2012, 02:58 PM	#13
Brockway Join Date: Nov 2011 Location: Sicily, but from Texas Posts: 56	Bought it. $35 shipped USPS priority is the cheapest I've seen, 21 pounds is about $33 at current exchange rates. Will be months before I can install it since I'm out of the country, but should be fun to mess with.
	0

03-02-2012, 03:05 PM	#14
Frog Join Date: May 2008 Location: Hampshire England Posts: 191	$35 is a good price Definitely a better carb that the original - instant starting and rock solid slow tick over + more performance. I Just need to sort my mis-fire / rev limit problem.. Frog
	0

03-04-2012, 06:59 PM	#15
Plukey Join Date: Nov 2011 Location: Poquoson Va Posts: 73	Gentlemen, Since my last post, I removed the carb & I had 32.5 slow & 135 main. As pictured above we can all agree it looked really rich..... I went down to 115 main & 25 slow as Weldangrind suggested. I had a little trouble starting the bike; it took a few extra turns than before to fire up, so I decided to go up on the slow to#30. Put it all back together & it fired up great mid throttle ran smooth, it maxed out at 60 mph no bucking or kicking. I didn't do a plug chop yet...but I think itâ€™s finally getting close! Iâ€™m happy with this adjustment. Frog....I just bought Different Jets from www.Jetsru.com as Weldangrind suggested..Purchased slow jets from 20 - 40 increments of five, & 110 - 150 main. Alot of jet changeing.. carb on & off..... My bike feels & sounds like it maxes out at 60 mph; Iâ€™m not always going that fast cause I'm normally in the woods on trails. But 55 mph is smooth and it handles great at those speeds. i wouldnt expect anymore than that out of a 200cc bike... Please keep us posted on any break thru's you may have. Weldangrind, I keep reading that the weather makes a difference, Hot air Vs cold air when I did these changes it was around 40 degrees.. When it hits 70 & above in the upcoming months here in Virginia will it run richer? What are your thoughts?
	0