Won't rev past 1/4 throttle under load - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
 
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post #1 of 9 (permalink) Old 04-06-2015, 11:59 AM Thread Starter
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Won't rev past 1/4 throttle under load

Hi, I've got a 2007 Vstar 650 custom.
Bike was running fine.
Now it runs rough, sputters, no power when I open up the throttle. ONLY under load. While idling it's fine.
I have gone through the carbs extensively.
It seems like a fuel issue (lean), but opening the choke doesn't help. And I'm tired of cleaning this carb. Main jets, tiny passages and orifices are clean and clear.
This lead me to believe it was electrical.

So,I have checked all electrical components.
ONLY problem I have found so far is this:

I have found the relay assembly 5KS-81950-00-00 has no continuity through the diodes (in either direction). This being said, those diodes provide a path to the ignitor. The ignitor controls spark, advance, etc.

I have ordered a new relay, but meanwhile, I was wondering if anyone else has had this issue.

The ignitor unit assy 5SC-82305-30-00 might be suspect as well, but only the dealership can check that, and it's expensive.


****SOLVED!! Intake crack..see post below

Last edited by Madness; 04-10-2015 at 09:09 PM. Reason: Solution to problem
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post #2 of 9 (permalink) Old 04-07-2015, 08:28 AM
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The wire/diode/relay doesn't make sense, cause then it wouldn't be running at all then, right? Not to assume here, but you know when checking diodes you need a digital multimeter set to the diode function, measuring voltage drop going across the diode. You can't set the multimeter to continuity/ohms, it'll read nothing both ways. Well you may get a number, or 0/OL signifying polarity. If you do not have a diode function on a multimeter, you can use a battery to provide power. Setting the meter to ohms only tells you the polarity to find which side of the diode is the anode and cathode. All I get searching the part number is that its a relay assembly, pretty complex with 11 connections. So being a relay, certain connections won't be closed until power is applied. Of course, I haven't researched it like you, so what connection goes to what I don't know. But its working starting up/idling, I can only assume its working fine. But I don't know for sure.

And the advancing shouldn't be an issue. In fact, should be less advance under a load. That characteristic is usually problems with idling, yours is the other way around.


So lean issues, ignore the carb. Check for air leaks? As much as I'm assuming you've fiddled or removed the carbs, think there might be a tear in the intakes? I had a pretty small holes in my air intake you really couldn't see until you started to pry and bend it then they opened up. On my 06 650. Your 07 is 8'ish years old, how many miles? Those rubber boots don't last.

I seem to be cursed with small engines rubber intakes. ATVs, my last bike. Just something to check, think air leak, not fuel lean, but too much air. And or, air leaks past the carb (intake), therefore not pulling enough of a vacuum on the carb drawing enough fuel.

Just something to try.

EDIT: oh, possibly check the lines and on/off/res switch for gunk too.

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Last edited by Mr Schaefer Pants; 04-07-2015 at 09:12 AM.
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post #3 of 9 (permalink) Old 04-07-2015, 09:54 AM Thread Starter
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Air Leak

I went through the fuel petcock.

The airleaks are something that may need more investigating. Everything looked ok, but maybe I need to shoot some carb cleaner at it and see if the idle changes (indicating a leak).

As for the relay,I used the diode setting although I'm going to check with a better meter tonight. Funny how the service manual just tells you to check continuity.
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post #4 of 9 (permalink) Old 04-07-2015, 10:36 AM
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Air leaks are always a tricky PITA. They might 'stay closed' under most circumstances, but something like the engine being under load may cause it to finally open up. Crud build up might keep it sealed until you bump it.

Hope ya figure it out, I hate troubleshooting.

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post #5 of 9 (permalink) Old 04-08-2015, 09:39 AM Thread Starter
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Air Leaks

You should be called "Mr Smarty Pants" respectfully.

I took your advice and squirted carb cleaner on the intakes while it was running. And, I found a consistent spot where the engine would bog down almost to the point of stalling.

Those intakes are spidered with cracks on the outside, but the inside shows none (therefore I assumed they were fine).

I couldn't find the crack on the inside, but clearly the carb cleaner was entering the back, halfway up, the rear cylinder intake.

Part on order. I hope this is my problem. I will keep people up to date on the solution as alot of other interweb posts seem to have the same issue.

On a side note, upon checking those diodes again, I dug out the service manual and noticed they don't tell you that you're checking a diode(only say look for continuity). Luckily I was using the schematics and knew there were diodes in the relay. ALSO, the manual has you checking them BACKWARDS! Be warned. Use the diode setting people, and follow the schematics in the back of the service manual, not their test procedure.


Anyone know where to get parts overnight? Dealers in Vegas are horrific about parts.
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post #6 of 9 (permalink) Old 04-09-2015, 06:43 AM
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I had similar boots on my bike (external cracks inside looked fine)

I changed both out and redid all the vacuum caps and band clamps.

Made a world of difference.

2000 Vstar 650 Classic , Firethorn orange Metal flake Urethane, OEM tall Windshield, 47 Harley Tail light mod, progressive springs, hard bags painted to match w/chr. bullet accents Custom Modified rear rack/backrest, Cobra Modified exhaust w/ chrome Pencil tips, Hyper charger kit,
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post #7 of 9 (permalink) Old 04-10-2015, 09:07 PM Thread Starter
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Smile Solved !!

It was the tiny little cracks in my rear intake boot.
Although invisible from the inside, the carb cleaner test pinpointed it.
Funny how the littlest leak killed the throttle under load.

New intakes and o-rings and the bike runs great again...

Thanks !!
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post #8 of 9 (permalink) Old 04-10-2015, 09:35 PM
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The facts were there. It just took the light to see them.

Being it was leaking as the demands at higher rpm increased the AFR
leaned out due to the leak at only the rear cyl. Imbalance between cylinders can cause all kinds of issues.

As you see now everything was ok except for the rear boot leaking.

An easy fix when you know what to do and look for.

Glad you got her back to normal. Priceless !

2000 Vstar 650 Classic , Firethorn orange Metal flake Urethane, OEM tall Windshield, 47 Harley Tail light mod, progressive springs, hard bags painted to match w/chr. bullet accents Custom Modified rear rack/backrest, Cobra Modified exhaust w/ chrome Pencil tips, Hyper charger kit,
PRV 15, Riser mounted speakers, Chrome levers,Fringe grips, studded Leather bib with pocket, Billet Oil filter relocation kit , 3.5 PMS w/ stock pilots, mains- 122.5, Custom billet t signals
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post #9 of 9 (permalink) Old 04-11-2015, 08:12 AM
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Awesome, glad you got it fixed!

I've never been a fan of rubber intakes, heat and time destroy them.

.:'09 Vstar 950T:.

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