[DraganTine]

Hello All

I have been going through the forums trying to go through and eliminate my starting issues and looking for a bit more help... Here's the low down so far..

Parked the bike after a ride with a just filled tank of gas - Garage Kept - Bike sat for aprox 3 weeks. I tried to go start it one day and wouldn't start seemed like a low battery so I got a trickle charger and let that sit for a few days. Came back and again kept cranking, backfired a few times - scared the crap out of me - but finally started and I took it out for a quick 5 min ride and parked it back in garage, hooked up the charger again.

A few days later same story cranked no luck backfired and drained the battery down so I quit. Decided to read what I could to see what was going on...

I took the battery out - It's an sealed battery MF says gel on it also - had it checked and charged by Autozone. I put it back in hours later, cranked backfired finally started went for a ride. I turned the bike off a coasted and tried to start it up, it wouldn't turn over. So I popped the clutch and it started back up. I repeated this a few times and it wouldn't start with the starter. I went back home and turned the bike off. Let it charger again. Few hours later, I checked the vent tube for the gas tank and left the gas cap open and tried to start. Thinking it was vacuum locked and wasn't getting gas. Again backfired barely starts let it run for a few cut it off. Tried to restart no luck just cranks a few backfires and I quit - Man them backfires are loud !!

Next day decided to check the voltage of the battery as I cranked it up 12 Volts when I put the MulitMeter on the battery. I cranked and it dropped down to 11 to 8 to 6 volts bouncing around. So I went and got a new MF battery just to check and it reacted the same way voltage drop and backfired. Went got my battery back and bought new NGK Iridium plugs put them in no luck still backfires. I took an old plug and connected them up to see if I have spark. The front cylinder fires on both plugs but looks weak light blue spark. The rear cylinder sparks intermittently and seems to backfire on that cylinder when it sparks.

This whole time I have always felt the starter was struggling to turn. Its not a solid cranking noise more of a rut-rut-rut-eeee-rut-rut. Not like a car or lawn mower like I use to repair a strong cranking wirrrr type noise....

I'm thinking of repair the starter at this point but was looking for more insite...


Thanks for any help.
Hope this isn't too long I tried to be as detailed as possible.

DT

 

[Knifemaker]

When you do try and start it, exactly what are you doing? Are you using the choke? Are you using the throttle?

The rear firing "intermittently" is not a good sign. Check the wires and connections to your coil. Are you sure the gas is good?
Air filter clean?


Look up the pickup coil mod here....

 

[wmsonta]

Are you sure you have a hot battery? This sounds identical to mine before I replaced the battery. Wouldn't start and sounded like a shotgun, had to jump it.

 

[new rider 9984]

You mau also be flooding the engine due to a internal leak in the petcock too much fuel in the cylinders can cause the engine to bog when trying to get it started

 

[DraganTine]

More info

Ok, I've had some time to finally try some more stuff....

Knifemaker - I'm trying to start from a cold bike usually in the mid afternoon pulled out of the garage in to Florida's 80's - Full choke not throttle - then crack the throttle a little when it won't try to fire after a few minutes of cranking. That's the ways its been since I'm having the problems trying to start the last 3 to 4 times now. Gas was new fill up now 5 to 6 + weeks ago but haven't added any additives / stabil ... Trying Coil Mod... See the rest of this post...

wmsonta - Yes it should / seems to be a good battery / Also I did try to use a new battery from Autozone - Another Sealed MF Battery - Same exact symptoms and test results as above 1st post.

new rider 9984 - I dont think its flooding I did some testing today see the rest of this post

Thanks for the help so far guys...

Ok today I did some more testing I looked at the coil mod and tested like he says I have over 12 volts at the battery (12.7) and the front coil is 12.4 the rear is 12.2 that's testing the red lead off the coil to the frame / battery neg terminal. I was wondering what the black and green leads goes to that's on the front and rear coil because I tested the red and black then the red and green leads together and it was 10 volts in the front and rear was 9. So I thought I thought I'd make a ground off the black and green leads to the frame - that resulted in NO spark what so ever on the front and back plugs.

I removed the ground I thought might help and recheck the spark with the new NGK iridium plugs it was a bit brighter and the rear seemed not to be missing as before maybe moving the wires around helped with a ground issue or I don't know... but I was getting good spark it looked like...

Ok so going with fuel now. The more I read backfire is a very lean mix / low fuel. so I took the tank off and looked at the petcock and the vacuum lines. the petcock seemed clean and I used some extra line and tested the vacuum lock to see if it let fuel flow, it did. I just used my finger to test the vacuum line on the carb, I cranked the bike and the vacuum sucked on each turn it was more of a vacuum pulse but I assume it will work to let fuel flow. I took the plugs out after several fail attempts to start and really looked at them I thought they were wet from the last few times before I tried but they seemed very bone dry this time. So I clean them up and reinserted and tried cranking again no luck and when I removed them they seemed just as dry when I took em out. So I'm thinking a carb rebuild or stuck float needle now ....

I just tried some starting fluid but I don't know if I got enuf down it the cylinders ...and it never started ... bah

Any one else think so...

How hard is it to rebuild carbs sync them ???

Also when I took off the air box intake to look I found this small rubber grommet about the size of a 1/2 dollar in the throat of the carb I think it out of the air box but not sure I have to pull the tank again and look how the air box comes out can be moved ...

Thanks
Brian

 

[kc2dgq]

COILS:
The ground is the pulsed signal to the coils, so grounding them will be NO SPARK. what you should do is possibly tie battery directly to the positive lead of the coils to ensure proper voltage (bypassing the wiring harness)....but if it runs, then it's probably not the issue.

I would consider the Pick Up Coil mod...reducing the gap on the magnetic pickups to increase the signal going to the ignition system.

That rubber o-ring you are showing looks a lot like the one on the bottom of the airbox where the hose coming from the emmisions valve for the air injection system enters the airbox (should be a hole in the airbox on right side of bike near the rear)

The vacuum line from the carb to the petcock is pulsed, but should be enough to keep fuel flowing as long as the other vacuum port on the second carb is not sucking air. Ensure the hoses are not split or damaged. If you removed the emissions stuff mentioned above, one vacuum nipple on the carbs should be capped off. you cold even tie both vacuum lines to the petcock through a "T" connector for a more constant vacuum to the petcock.


it sounds like either not enough fuel, or the rubber boots on the carb intakes are leaking and allowing too much air....causing a lean condition.


ALSO....check your vent line and gas cap vent for the gas tank. not air in=no fuel out....open the cap and see if that helps to allow fuel flow.

 

[VN750Rider/Jerry]

Maybe not that bad, but mine has always been harder to start than I think it should be since it was new. I think the main problems with the bike are a weak starter and a weak ignition system. Even with a battery that will start a Peterbilt connected to it, it still cranks slow. I don't think it has much of a spark at that cranking speed. The pickup coil mod might help. Now with the advent of ethanol gas, things get even worse. If mine sat there for 3 weeks with gas in the carbs, it would be almost impossible to start. The gas evaporates, leaving ethanol and water in the bottom of the carbs where the jets are, and that is what gets sucked into the engine when you try to start it. If I know mine is going to sit for awhile, I drain the carbs and fill them with WD-40 to prevent ethanol corrosion. If I do forget to do that, I always drain the carbs, and flush them out with fresh gas before trying to start it. I also keep it on a battery tender.

 

[Goofyfoot2001]

I didn't read the whole thing, was the ignition switch cleaned?

 

[kyledk]

I had this same issue, before the stator went out. I found out the stator was bad when I drained the battery trying to start her. I'm hoping it was just weak voltage, but even when we put a jump pack on it my bike doesn't want to start. No so good, might have some extra work to do while I've got the engine out.

 

[DraganTine]

Well,

After all that I just broke down and bought a new starter, I had a feeling it was sucking too much from the battery to start it also sounded kinda funny...

I got this one off ebay (I cant post url not enuf posts) Auction # 301262039444

It starts great really quick no more rut rut rut a quick rumm rumm and starts easy. just had a weird feeling but the old starter seated a bit different then the new one the old one pushed all the way in to the bike and it sat deeper than the new one there is a small open space from the face of the starter to the engine case. it seals fine no oil leaks but I just thought it was weird but no problems at all the starter has a year warranty so that good also ....

Long story short I'm back riding
Brian

 

[DraganTine]

Well,

I broke down and bought a new starter I seemed to drag so I replaced it. the old oen sorta rut rut rut no go the new one has a bit more power a rummm rummm and starts up easy from a cold engine full choke no throttle. once warm no choke no throttle and starts up with the easiest touch to the button.

I just have this weird issue the old starter sat a bit deeper then the new one there is no oil leaks but the face of the new one has a bit of a gap between the engine case them mounts went well and the o ring seated good but it just seems weird any one else have this or did I get some thing wrong.

I got this on off ebay (cant post link too few post ) auction # 301262039444

As I said it seated good no leaks but just a bit of a gap there ..... I might get a photo later to show ( just too tired right now )

Thanks Brian

Long story short back in the wind

 

[JM2001]

Sounds like a bad stator or a bad regulator/rectifier. Check the 3 stator wires and see if you are getting over 70 volts AC on each leg. If you do, check the rectifier leads going to the battery and see if you are getting 14 volts DC @ 4000 rpms going to the battery. One of the two is not supplying enough voltage.

 

[DraganTine]

Humm...

OK I tried 2 times last night to post with a small pic of the starter it said needed Mod review .... Never showed and I have posted before and never had to wait for mod authorization....

Long story short got a starter since thought it was struggling now cranks cold fast runs fine ...

Wish my other post would show up at work so cant do much from here ....

Brian

 

[Goofyfoot2001]

Excellent, let us know when it stops starting hot

 

[khaisvt]

Right now I'm scared lol... I tried to get the 750 started since sitting since august. Was running well before then it just decided to flood the cylinders and the carb. Today i got it to run and i held my hand on throttle from like 2-3k rpms steady because everytime i let go i think it wanted to die. I didn't wanna take a chance and let go just incase it did i wanted to get the fluids circulated. Then after it slowly dropped, i tried revving it and it died. I tried to start it again and i got so scared. It was either from the front cylinder or both cylinders. A huge flame popped out the bike. Not from the exhaust but from the spark plug holes and i felt the heat. im ok tho i didnt get a burn or anything. When i mean a huge flame I remember it was orange. Came out the spark plug hole im pretty sure. Not sure what this means. I did put starting fluid in it yesterday. Could that be because theres a little too much? No clue I hope someone can help!

 

[Spockster]

Right now I'm scared lol... I tried to get the 750 started since sitting since august. Was running well before then it just decided to flood the cylinders and the carb. Today i got it to run and i held my hand on throttle from like 2-3k rpms steady because everytime i let go i think it wanted to die. I didn't wanna take a chance and let go just incase it did i wanted to get the fluids circulated. Then after it slowly dropped, i tried revving it and it died. I tried to start it again and i got so scared. It was either from the front cylinder or both cylinders. A huge flame popped out the bike. Not from the exhaust but from the spark plug holes and i felt the heat. im ok tho i didnt get a burn or anything. When i mean a huge flame I remember it was orange. Came out the spark plug hole im pretty sure. Not sure what this means. I did put starting fluid in it yesterday. Could that be because theres a little too much? No clue I hope someone can help!

Were the plugs removed when you saw the flames?

We're the plugs installed and tight?

Are you sure the flames came from the spark plug holes?

Did you have Seafoam in the gas when you parked it in August?

With the plugs removed, it can be normal to see flames especially if there's some excess gas in the cylinder.

 

[khaisvt]

My dad said he took the plugs out to see if they had any gas/oil on them. Im pretty sure it did if anything it came from the front part of the bike. The plugs were not removed when i saw the flame. But it was a huge flame. There was not seafoam in the tank. I drained all the gas i could get out and filtered it back into the gas can.

 

[Spockster]

My dad said he took the plugs out to see if they had any gas/oil on them. Im pretty sure it did if anything it came from the front part of the bike. The plugs were not removed when i saw the flame. But it was a huge flame. There was not seafoam in the tank. I drained all the gas i could get out and filtered it back into the gas can.

You might check to make sure the plugs are snugged tight, you don't want them squeaky tight, just snug. If they were even slightly loose fire could make it out of the combustion chamber.

It's happened a few times that the plugs didn't get all the way tight because the socket can drag on the plug tube.

Is the bike earshaved or stock? It's possible to get vapor built up in the stock airbox and flame could be forced out if it backfires through the carb . There's been cases on other bikes where the airbox got blown to pieces.

Sounds like the fuel situation may be ok. I was thinking it might have clogged jets from old gas, but not if you drained the carbs.

Often, when carbs sit with no gas in them, the float valve can stick open, causing it to flood.

 

[khaisvt]

Yep, when I was taking out the carb, you remember a few months ago when i made a form i was told i can shave the ear. I already spend about $30 bucks on the fittings for that air box so i didnt want it to go to waste. The airbox is not ear shaved. I didnt drain the carb, i think when my dad bought a used carb for this 750 the old owner tried rebuilding the carb or draing the carb, He did something because the bolt is hex bolt is stripped. No clue how to get it out, it was dripping gas from the little drain hole. I put some gas-resistant sealant in the whole and the leak stopped. Talking about the vapor... I dont have the airbox components connected like the part from the carb or the parts in front of the bike connected up.

 

[Spockster]

Yep, when I was taking out the carb, you remember a few months ago when i made a form i was told i can shave the ear. I already spend about $30 bucks on the fittings for that air box so i didnt want it to go to waste. The airbox is not ear shaved. I didnt drain the carb, i think when my dad bought a used carb for this 750 the old owner tried rebuilding the carb or draing the carb, He did something because the bolt is hex bolt is stripped. No clue how to get it out, it was dripping gas from the little drain hole. I put some gas-resistant sealant in the whole and the leak stopped. Talking about the vapor... I dont have the airbox components connected like the part from the carb or the parts in front of the bike connected up.

Ok, it sounds like maybe the carbs were open, not connected to filters or the airbox. In that case a carb backfire would make a fairly large flame.

Gas can evaporate out of the carbs when parked a while. As little as one month, even less in hot weather.