Main Jet replacement
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Intermediate
Joined: Feb 2016
Posts: 32
Likes: 0
From: Bath
Main Jet replacement
OK need a bit of help here. Have a 1986 Heritage which was imported to the UK from the states. It is very original with the plug in the Carb to prevent "tuning" the mixture screw. It's coughing very badly when the revs increase and running very lean (white deposit on plugs) we are wondering if the main jet should go up to enrich the mixture it currently has a 170 main jet. Are they easy enough to find for this year carb.
Cruiser
Joined: Aug 2010
Posts: 181
Likes: 13
Could be the compliance fittings ,manifold to head. Definitely pull plug to access mixture screw and increase low speed jet 1 to 2 sizes. Main jet is pretty close from factory ,you would have to do a high speed run test to check main.
Road Captain
Joined: Dec 2014
Posts: 723
Likes: 376
From: Daytona
It's NOT the main jet. As stated, check the compliance fittings, they are probably leaking.
That said, there's nothing you can do to that carb to make the bike run perfect, it's just a lousy carb. Switch it out to a later CV, S&S or Mikuni carb, that'll wake that old EVO up.
That said, there's nothing you can do to that carb to make the bike run perfect, it's just a lousy carb. Switch it out to a later CV, S&S or Mikuni carb, that'll wake that old EVO up.
Road Warrior
Joined: Dec 2009
Posts: 1,328
Likes: 154
From: Lake City, Florida
I had a EVO powered stock carbed Heritage back in the '90's if I remember right, just drill a little hole into that plug and then pull it out with a spring hook or pry it out. It's blocking the low speed fuel mixture screw, turning the low speed mixture screw counter clockwise will richen your low speed fuel mixture. The main jet is for high speed fuel mixture (4000-5000 RPM). You won't need to change the main jet. You can also adjust the needle it affects the mid range. I think lowering it richens the mixture. If I remember right??? Their's probably good videos on youtube.
Last edited by jamesroadking; Mar 1, 2016 at 05:06 PM.
Seasoned HDF Member
Joined: Jun 2010
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From: Upstate New York
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Club Member
Joined: Jun 2007
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From: Bedford UK
Hello old chap, from just up the road and welcome to HDF! I suspect you have other problems, as suggested above, so leave messing with the carb settings for now. If you remove the carb to check it over, buy a refurb kit, which comes with all gaskets and rubber parts etc.
For a useful source of parts diagrams and info try this website.
For a useful source of parts diagrams and info try this website.
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Thread Starter
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Intermediate
Joined: Feb 2016
Posts: 32
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From: Bath
Hi Everyone and thanks for useful suggestions. We took the carb apart for ultrasonic clean. All seems good within the carb. Checked all gaskets and again all looked good. Will check our work again. Is there a seal for the Fast idle Cam (compliance fitting)? I don't think we took that bit off.
Wondering if to upgrade to the later CV version… although I would like to keep the bike original if i can.
Wondering if to upgrade to the later CV version… although I would like to keep the bike original if i can.
Dirt don't hurt
Joined: Jan 2011
Posts: 21,066
Likes: 4,568
From: Haslet Texas
Hi Everyone and thanks for useful suggestions. We took the carb apart for ultrasonic clean. All seems good within the carb. Checked all gaskets and again all looked good. Will check our work again. Is there a seal for the Fast idle Cam (compliance fitting)? I don't think we took that bit off.
Wondering if to upgrade to the later CV version… although I would like to keep the bike original if i can.
Wondering if to upgrade to the later CV version… although I would like to keep the bike original if i can.
While I've never had a butterfly carb many here have said that the CV is a much better carb.