#68 Delortto Jet swap

ibcnya

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Oct 29, 2008
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Swapped out my stock main jet out for a #68 and what a difference. Better accel and higher speed up top. Thought I would share im stoked for now....

 

ibcnya

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Oct 29, 2008
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Concord NC
That's just a hair smaller than stock. Cool.
I thought stock was a #70(.028) or so this chart says it should be bigger......

http://motorbicycling.com/attachments/f13/2554d1221495729-ht-main-jet-size-drill-size.jpg

Either way im running the needle clip on the 3rd slot from the bottom and that got rid of the [email protected] bog, it also fixed the top end studder.

Question though...I wanted to go a step bigger what should I have gone with? Are the tables backwards or something?
 
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Pablo

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Dec 28, 2007
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I thought stock was a #70(.028) or so this chart says it should be bigger......

http://motorbicycling.com/attachments/f13/2554d1221495729-ht-main-jet-size-drill-size.jpg

Either way im running the needle clip on the 3rd slot from the bottom and that got rid of the [email protected] bog, it also fixed the top end studder.

Question though...I wanted to go a step bigger what should I have gone with? Are the tables backwards or something?
The tables are in drill # size. Can't confuse that with Del Orto part #'s (which are in .XX mm). I'm running a part #65 which works great.

Stock is .70mm.
 

ibcnya

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Oct 29, 2008
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The tables are in drill # size. Can't confuse that with Del Orto part #'s (which are in .XX mm). I'm running a part #65 which works great.

Stock is .70mm.
So youre running a 80mm? Im confused....the chart says the #68 is .78mm, is this wrong?
 

Pablo

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Dec 28, 2007
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So youre running a 80mm? Im confused....the chart says the #68 is .78mm, is this wrong?

Indeed that is not correct. Your thinking is not right. "Designation" does NOT mean Del Orto part #'s. It means industrial number drill sizes. The table is for general usage and really just tells you drill bit equivalents, NOT Del Orto jet #'s.

Mine is a Del Orto #65 which is .65mm. Your is a #68 which is .68mm. Stock is .70mm which is the same as Del Orto #70

This is NOT a bad thing. The thought is the these engines will run better (as you are seeing and feeling) by being slightly lean of stock. Good blind experiment!!
 
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ibcnya

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Oct 29, 2008
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Indeed that is not correct. Your thinking is not right. "Designation" does NOT mean Del Orto part #'s. It means industrial number drill sizes. The table is for general usage and really just tells you drill bit equivalents, NOT Del Orto jet #'s.

Mine is a #65 which is .65mm. Your is a #68 which is .68mm. Stock is .70mm

This is NOT a bad thing. The thought is the these engines will run better (as you are seeing and feeling) by being slightly lean of stock. Good blind experiment!!
Ok......by what you are saying Delortto uses the jet size as the listing number. Basically take the number a convert it to mm. I feel that the 70cc would thrive with a bigger carb as well. Ive been doing alot of research and alot of what im gathering is that you want at the least a 17mm carb on a 70cc. The 14mm is made for the 49-50cc and just wont supply enough air to help the engine get to its full potential.
 
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ibcnya

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Oct 29, 2008
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Either way im running the needle clip on the 3rd slot from the bottom and that got rid of the [email protected] bog, it also fixed the top end studder.

?
Studders back again....I hate the stock carb on these things. Everyday my bike runs different and I have to make a adjustment to something. I dont get it, really, one day its great the next its crap. Another thing that bugs me is the sorry carb slide cap. It wont even stay tight without tape around it. I work on this thing more than I ride it, really.....I shoulda bought a scooter.:(
 

POPS

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Sep 8, 2008
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Studders back again....I hate the stock carb on these things. Everyday my bike runs different and I have to make a adjustment to something. I dont get it, really, one day its great the next its crap. Another thing that bugs me is the sorry carb slide cap. It wont even stay tight without tape around it. I work on this thing more than I ride it, really.....I shoulda bought a scooter.:(
That could be your problem. Carb slide cap. One time sucking air. Next time not...POPS
 

ibcnya

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Oct 29, 2008
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That could be your problem. Carb slide cap. One time sucking air. Next time not...POPS
Considering this I used a tire tube to make me a oring for the carb cap. It tightens up nicley now and no longer loosens itself up. Studder problem is still there though. If I kill the petcock when it starts studdering the engine will run nicely. Im still thinkin its getting to much fuel. Considering a smaller jet, maybe a #65. Ill keep you guys posted on the outcome.

BTW the bike has been running great at times and running down cars running speeds of 40mph, passing a car at that rate is great.
 

Josh380

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Feb 13, 2009
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Aliso Viejo, CA
Sorry if this is a stupid question, but is this a simple mod for my stock carb? Can I buy one of these jets and experience better performance, or will I need a different needle as well?
 

ibcnya

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Oct 29, 2008
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Just swapping the jet made a really big difference in the way the engine ran up top. I think a #65 with a lower clip positoin on the needle and itll run really great. With the #68 my bike runs over 40mph, but still experiences some top end studdering and missing which can be resolved by turning the petcock to the off position(limiting the amount fuel going in). The leads me to believe that while the #68 helps the engine to run better its still getting to much fuel. Though on some days its fine, others it runs crazy. Cheap parts means limited tuning.

Yes though the Dellorto 1486, jets fit rite in the china carbs.
 

Josh380

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Feb 13, 2009
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Just swapping the jet made a really big difference in the way the engine ran up top. I think a #65 with a lower clip positoin on the needle and itll run really great.
Lower clip position? In other words, moving the clip down one from stock or up one, because I've already moved the clip up one from the stock position, it runs better than it did, but I can still see some room for improvement. The motor almost seems like it's hesitating near the top end..like it wants to go faster but can't. I notice the bike feeling like it ever so slightly slows down then immediately tries to go faster. Not sure if that describes the "bucking" sensation that some people notice.........
 

ibcnya

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Oct 29, 2008
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Concord NC
Lower clip position? In other words, moving the clip down one from stock or up one, because I've already moved the clip up one from the stock position, it runs better than it did, but I can still see some room for improvement. The motor almost seems like it's hesitating near the top end..like it wants to go faster but can't. I notice the bike feeling like it ever so slightly slows down then immediately tries to go faster. Not sure if that describes the "bucking" sensation that some people notice.........
Bucking as in studdering, you are gettin to much fuel in there. Id try finding another jet to put in the carb. My #68 works good but not great. Pablo swears by his #65, which is what im waiting on to arrive in the mail.
 

Josh380

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Feb 13, 2009
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Aliso Viejo, CA
Bucking as in studdering, you are gettin to much fuel in there. Id try finding another jet to put in the carb. My #68 works good but not great. Pablo swears by his #65, which is what im waiting on to arrive in the mail.
Ok, so what I've described accurately points to too much fuel? Where do I get the #65 jet?
 

ibcnya

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Oct 29, 2008
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Concord NC
#65 jet with the needle clip on the 3rd slot runs great. No idle-WOT bogging and no missing on the upper rpm range. Running a consistent35-40mph.