Would a tech guru please explain this to me... - Honda Shadow Forums : Shadow Motorcycle Forum
 
LinkBack Thread Tools
post #1 of 10 (permalink) Old 05-27-2008, 10:54 PM Thread Starter
Member
 
Ohio Tom's Avatar
 
Join Date: Apr 2008
Posts: 41
Would a tech guru please explain this to me...

I'm baffled by my 83 750!

Starts fine, revs at a standstill to redline smoothly, as soon as put in gear--even on the centerstand, i.e. little load--the bike revs to 3500 rpm then bogs and pops and won't rev further!

What changes when in gear? Is it electrical?

Doesn't reving fine (all throttle positions) in Neutral mean all of the three carb circuits are working?

For those that know my history--know I want this Shadow to work after all I've done to get it to this point (with lots of good info here, btw). But honestly, I'm getting tired of this crap... Thing is it fits me like a glove and has tons of character, and handles great, etc. BUT if I can't ride it on the highway....

Hell, I looked at a Ninja 250 today for sale!

BTW...
Fresh NGKs,
Fresh Air filter foam,
no vaccuum leaks,
fresh carb cleaning & Dynojet

I'll hang up and listen to your reply...


Tom Pardi
Cincinnati, OH
--
1983 VT750C
1982 GS550E
1981 GS450L
Ohio Tom is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 05-27-2008, 11:09 PM
Member
 
Join Date: Sep 2007
Posts: 48
bad coil or plug wire if i had to guess ...quick example my truck yah truck was studdering to all hell and back cruising so (under load) but i could rev it no probs just sitting in the driveway to redline .....found out a bad plug wire was the cause..

Definately sounds electrical

Good luck

baddger222 is offline  
post #3 of 10 (permalink) Old 05-28-2008, 07:51 AM
Senior Member
 
tubes_rock's Avatar
 
Join Date: Jun 2006
Location: Northern NH
Posts: 5,234
Revving in neutral does not at all mean that your carbs are working okay. Remember that to get a bike with no load up to redline only takes 1/8 throttle. At that point, the pilot jet has barely started to enter the scene. Nevermind the needle jet!

Sounds to me like a classic case of a clogged carb. Your idle mix is doing all the work, even up to redline, if you're not making the engine do any work.

When you're actually trying to accelerate the bike, then the other jets come into play, and it sounds like one or more of them isn't letting the fuel through.

Time to take the carbs off and find out what's not working right in there.

--Justin

Currently Running Stable:
2010 Honda NT700V
1986 Shadow 700
1986 Honda Trail 110 (Postie Bike)
1987 Honda Rebel 450
1973 Honda Mini Trail 50
tubes_rock is offline  
 
post #4 of 10 (permalink) Old 05-28-2008, 09:24 AM
Senior Member
 
litnin's Avatar
 
Join Date: May 2004
Location: Dallas, GA
Posts: 3,761
Quote:
Originally Posted by tubes_rock
Revving in neutral does not at all mean that your carbs are working okay. Remember that to get a bike with no load up to redline only takes 1/8 throttle. At that point, the pilot jet has barely started to enter the scene. Nevermind the needle jet!

Sounds to me like a classic case of a clogged carb. Your idle mix is doing all the work, even up to redline, if you're not making the engine do any work.

When you're actually trying to accelerate the bike, then the other jets come into play, and it sounds like one or more of them isn't letting the fuel through.

Time to take the carbs off and find out what's not working right in there.

--Justin
+1

Along with that, if you have a fuel filter, check it.
That's a classic clogged fuel filter sign.

Gasoline is for washing parts, Alcohol is for drinking... NITRO is for racing!
litnin is offline  
post #5 of 10 (permalink) Old 05-28-2008, 10:12 AM Thread Starter
Member
 
Ohio Tom's Avatar
 
Join Date: Apr 2008
Posts: 41
Thanks for the replies.

I have had the carbs off three times, been cleaned 3 times. I can blow through the idle jets, I just changed the main jets to the 120's that came with the Dynojet kit. I really need the breakdown on what carb circuit does what and how to check each jet. Since there has been no major change in performance since the re-jet maybe it's the fixed jet that is not adjustable?

The carbs have new gaskets, good diaphrams. New fuel filter.

I will look into the plug wires and weak coils and CDI boxes...
Need to check the timing and I wonder to what degree the carbon I saw on the valves visible with the carbs off has to do with this issue.

Tom Pardi
Cincinnati, OH
--
1983 VT750C
1982 GS550E
1981 GS450L
Ohio Tom is offline  
post #6 of 10 (permalink) Old 05-29-2008, 01:21 PM
Member
 
Join Date: Sep 2007
Posts: 51
This may sound silly but i had that same issue with my 600. Turned out that it was getting TOO MUCH air. The bike wont run if any of the air duct is missing or not seated correctly. Just make sure all the air intake is clamped down good and didnt slip off.

89 Shadow 600 VLX
eatumup is offline  
post #7 of 10 (permalink) Old 05-29-2008, 02:16 PM
JAT
Junior Member
 
Join Date: May 2008
Location: mn
Posts: 24
It does sound like a fuel starvation issue. Too much air = too lean. Plugged circuit = lean. What kind of shape were your old plugs in? What do the new plugs look like with their limited use? When I first read the post my thought was that I had the same problem on my snowmobile (granted it is a 2-stroke), and that it had a bad crank seal and kinked carb boot which led to a lean condition, and a melted piston. I have read other comments on a snowmobile forum that sound similar to yours and it ended up being a bad cdi box. There is a electrical troubleshooting flow-chart thing somewhere on the board here that may help you solve it if it is electrical. Good Luck!
JAT is offline  
post #8 of 10 (permalink) Old 05-29-2008, 02:42 PM Thread Starter
Member
 
Ohio Tom's Avatar
 
Join Date: Apr 2008
Posts: 41
The old (100 miles) NGK plugs were oil-fouled. I haven't checked the new set yet.

I do remember seeing the flow chart around here, will check it out. I noticed that the bike ran better with the choke on about 2/3 but then the tach started going haywire after a few miles until the bike cut out completely on me at ~30 mph.
Ohio Tom is offline  
post #9 of 10 (permalink) Old 05-29-2008, 04:16 PM
Senior Member
 
tubes_rock's Avatar
 
Join Date: Jun 2006
Location: Northern NH
Posts: 5,234
Oil fouled!?!?

A 4-stroke engine that's mechanically sound should never have oil fouled plugs! Were they wet, greasy black? Or just dry sooty?

If they were wet and black, then you better take care of the mechanical problems before you worry about your carbs!

--Justin

Currently Running Stable:
2010 Honda NT700V
1986 Shadow 700
1986 Honda Trail 110 (Postie Bike)
1987 Honda Rebel 450
1973 Honda Mini Trail 50
tubes_rock is offline  
post #10 of 10 (permalink) Old 05-29-2008, 07:39 PM Thread Starter
Member
 
Ohio Tom's Avatar
 
Join Date: Apr 2008
Posts: 41
Justin, Yeah, wet and black, not to the extreme, but of all of the conditions given in the Clymer manual, oil fouled is the best description.

The new plugs were better, light tan but still had oil on them.

I've got 3 oz. of SeaFoam in the crankcase too, FWIW.

In the process of trying to clean the carbon off of the valves with some Yamaha Ring Free ($17 a bottle--but looks to be some serious stuff) I wanted to get some mix through her well after about a half hour the tach went crazy again and she died.

Started right up but I noticed my fuel filter was feeding bubbles (my secondary f.f.) to the carbs and there wasn't much gas in there, so maybe my fuel pump is going.

After the tach went crazy the 2nd time, I pulled off the road about a mile from my house to check things out before the bike cut out again. I started off for the house and the clutch lever went limp.

Starting to wonder which of us will kill the other first.



Is there a guide to "Parting out" a bike on this board somewhere?

Ohio Tom is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda Shadow Forums : Shadow Motorcycle Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
please please please help me tc862011 Technical Discussion 22 05-03-2014 10:34 PM
low tech, tech tip CrazyDave General Bike Discussion 6 03-19-2012 08:03 PM
Can some explain the differences please Beachy Technical Discussion 2 10-23-2008 06:40 PM
explain please morepower General Bike Discussion 15 01-30-2007 07:16 PM

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome