All Things Moto! Web Forums

Go Back   All Things Moto! Web Forums > Specialty Riding Forums > Vintage Riding

     
Reply
 
LinkBack Thread Tools
  #1  
Old 03-24-2010, 02:39 AM
Beginner Class
 
Join Date: Mar 2010
Last Online: 02-02-2011 02:15 AM
Location: Utah
Posts: 8
Default 1982 Maico 490GS Carb Jetting

I have been rebuilding a 1982 GS 490 and need help with a starting point for jets on the new carb.

I put a Mikuni 38mm round-slide carb on the bike and I am running at 4000-5000 ft above sea level. I have tried a few setups but nothing gives me much although the bike starts fairly easily.

Idle is non-existant until I turn the idle adjust screw all the way in with every jet setup I have tried.

I do know how to do plug checks for lean/rich but have not found a sufficient starting point to even try a full-on plug test.

Thanks in advance for any help you can give me.
Reply With Quote
  #2  
Old 03-24-2010, 05:22 AM
Big Maico 393's Avatar
Super Moderator
 
Join Date: Jan 2003
Last Online: 10-29-2014 04:41 AM
Location: Kingwood,Tx
Posts: 4,481
Default

First off welcome to !

If you had the Bing Carb on your 490, I could give you the baseline jetting off the top of my head!

But Since you have a Mikuni you will need to join the Yahoo Maico group & ask the gang over there.
[Only registered and activated users can see links. ]

Or Call Mark @ Northwest Maico-CZ

Phone: 507-625-8602
Fax: 507-625-8605
Email: [Only registered and activated users can see links. ]
Reply With Quote
  #3  
Old 03-24-2010, 10:23 AM
Beginner Class
 
Join Date: Mar 2010
Last Online: 02-02-2011 02:15 AM
Location: Utah
Posts: 8
Default

Thanks, I sent out an email to NorthWest Maico.

I will let everyone know the reply.
Reply With Quote
  #4  
Old 03-25-2010, 12:32 AM
Beginner Class
 
Join Date: Mar 2010
Last Online: 02-02-2011 02:15 AM
Location: Utah
Posts: 8
Default

Here is what I found searching through the Maico Yahoo Group:

Jetting for 38mm Mikuni on a 81 490.

2.5 Slide
340 Main
Q-0 Needle jet
6DH3 Needle (clip positioned as required)
Air screw 3/4 to 1.5 turns off seat.

Mine is an 82 GS 490 but I would think it is close enough.

I will probably jet my carb to these settings this weekend and try it out. I will let you know how well this works.

I also assume this is for sea level, but I will do a few plug checks to make sure it is correct for my altitude.

Last edited by DuoDS; 03-25-2010 at 05:17 PM.
Reply With Quote
  #5  
Old 03-29-2010, 02:49 PM
Beginner Class
 
Join Date: Mar 2010
Last Online: 02-02-2011 02:15 AM
Location: Utah
Posts: 8
Default

I rejetted the bike this weekend with promising results.

I went with:

340 main
stuck with the original needle and needle jet, the one that came with my Mikuni VM38. the needle has a more gradual taper as opposed to the 6DH3 listed below which has almost no taper before the needle just ends.
42.5 pilot

Started on the first serious kick - with the choke on. Pulled the wheel up in 1st 2nd and 3rd gear.

Did not have the time or space to do plug checks, but this is the first time it has run well enough to even do plug tests
Reply With Quote
  #6  
Old 03-29-2010, 06:21 PM
Big Maico 393's Avatar
Super Moderator
 
Join Date: Jan 2003
Last Online: 10-29-2014 04:41 AM
Location: Kingwood,Tx
Posts: 4,481
Default

Great!

I was at the races yesterday & a new guy came out with a stunning 82'490 GS setup for MX.

It has the reed motor & it sounded great, I think that my friend got a picture of it, I'll have to check.
Reply With Quote
  #7  
Old 04-01-2010, 12:51 PM
cycleryan's Avatar
Intermediate Class
 
Join Date: Mar 2003
Last Online: 07-10-2012 06:50 PM
Location: Austin Texas
Posts: 245
Default

Yea , that thing was sweet!
Reply With Quote
Sponsored Ads
  #8  
Old 05-06-2010, 03:02 AM
Beginner Class
 
Join Date: Mar 2010
Last Online: 02-02-2011 02:15 AM
Location: Utah
Posts: 8
Default

I have some pics of my bike in action - but I "may not post attachments", so I guess they are not getting uploaded.

The jetting mentioned earlier in the thread is pretty good at around 4,000 ft in altitude, not so good at 6,000 where the bike would cough at WOT and then have to catch up with itself.

At 4,000 ft. it runs strong and does not sputter at WOT - the plug, however, is black (but dry) so I think it is still a little rich. Next time out, I will try it with a one step smaller main. That should do it.

Also, when the bike is warm, it is hard to start - don't know if that is related, but I need to look into that as well.
Reply With Quote
  #9  
Old 05-06-2010, 10:28 AM
Big Maico 393's Avatar
Super Moderator
 
Join Date: Jan 2003
Last Online: 10-29-2014 04:41 AM
Location: Kingwood,Tx
Posts: 4,481
Default

DouDS,

If the Maico gets harder to start when warm, I'd be looking at the ignition system to see if it still has a good spark. you might want to clean all the grounding points of the ignition system.

I know on the MX versions if that where to happen, I would be checking the Motoplat, but your GS has a Bosh system & I don't know about them.
Reply With Quote
  #10  
Old 05-07-2010, 12:10 AM
Beginner Class
 
Join Date: Mar 2010
Last Online: 02-02-2011 02:15 AM
Location: Utah
Posts: 8
Default

My Maico has a new PVL ignition that throws a fat blue spark every time it fires. A great upgrade from the original.

The reason why I think it could help on a warm start to go a little leaner is that trying to start the bike when it is warm, it often needs the compression release pulled in order to kick it hard enough to get the PVL to fire (PVL must spin fairly fast to work). When it doesn't start the first few kicks, there is always a serious amount of wetness around the compression release.

I guess this could be normal, but I just figured the warm engine was getting bogged down with too much fuel, perhaps fouling the plug.
Reply With Quote
Reply

  All Things Moto! Web Forums > Specialty Riding Forums > Vintage Riding


Bookmarks

Thread Tools


Similar Threads for: 1982 Maico 490GS Carb Jetting
Thread Thread Starter Forum Replies Last Post
jetting the raptor 350 carb chris99 ATV/UTV - Yamaha 8 07-20-2012 04:11 AM
1982 YZ 490 Carb jetting Abbie 2-Stroke Dirt Bikes - Yamaha 1 08-23-2009 04:25 PM
Mikuni Jetting & Ignition for 82 Maico 490 michida 2-Stroke Dirt Bike Forums 12 04-27-2009 05:55 AM
03 CRF450r carb jetting? blair1980 4-Stroke Dirt Bikes - Honda 4 03-02-2005 02:30 PM
PW 80 carb/jetting hmrland Mini Dirt Bike Riders 4 02-18-2004 10:00 PM


All times are GMT -6. The time now is 03:11 PM.

Portal Forums Photo Gallery Popular Tags

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright ©2002-2014, JDub Consulting, Inc. All Right Reserved.