Could these spark plugs cause hard starting?

[Shane0524]

I just finished rebuilding the carbs and replacing the fuel lines on my 1996 GTX with a stock 787 setup. The machine has 50 hours. When I took it out for its first test ride after the work it ran great. 7000 rpm no problem and 50+ mph. Here is the one issue though, it tended to be a bit difficult to start, it always did start but it seemed like after it sat for a few minutes it would take an extra few seconds of cranking to start. If restarted immediately it usually fired right back up. Then when it did start after sitting it would bog a little and be a bit smokey and then smooth out at normal idle. Once running it runs great. I was thinking that maybe there was some issue in the fuel system causing fuel to run back out of the carbs and therefore take a few more seconds to reprime the system when starting after sitting. But now I'm also wondering if my plugs are just in need of replacement? They came out of the engine a little bit wet around the edges but it had been idling a little before. The ends are dark brown/a little reddish. Anyone have and experience with a similar issue or an idea about what is going on? Do these plugs look normal?[video=youtube;iwx4WJJiyyU]https://www.youtube.com/watch?v=iwx4WJJiyyU[/video]

 

[racerxxx]

When you rebuilt the carbs, did you replace the needle and seats? If not they will over time(from 96) take a set and there will be an ever so faint groove around the rubber tip on the needle that seals the gas from trickling in when it shouldn't, thus giving a hard start after it's been running. When you had the carbs off to rebuild them did you make sure and check the oil pump alignment? When you disconnected the cable from the PTO (back carb) that is where the adjustment is, but there is an index mark on the pump and also on the oil pump cable lever that need to align. If it's not in the right place it will inject a bit more oil at idle. As far as the red, are you using any fuel additives?


Pic courtesy of kicker

 

[Shane0524]

Yes when I did the carbs I replaced needle and seats and set checked popoff, I also made sure to sync up the oil pump aswell. I'm just running some fuel stabilizer. Any other ideas?

 

[soccerdad]

Did you use Mikuni carb kits? I have heard some of the non mikuni kits have diaphragms that slightly hold the needle open. It will pop-off fine in the bench test, but when you assemble it, it may leak. Just a thought.

 

[Shane0524]

I used SBT kits.

 

[Austrian Rotax]

Soccerdad is probly right. while the carb is fully assembled pump your pop-off tester to 10 or 15psi if it leaks down some then that metering diaphragm is holding the n/s open slightly, I wouldn't be surprised since you used an SBT kit. As for your spark plugs ive seen slightly red electrodes, probly just the gas station you got your gas has a few odd additives in their gas those spark plugs look terribly rich, should be mocha brown but with all the fuel additives that some gas stations use these days reading sparkplugs is just an educated guess in fuel to air ratio.

 

[Shane0524]

Uggghh alright. Taking those carbs off again is the last thing I want to do right now! Is there a chance that those plugs are just in need of replacment and could have been causing a slightly hard start?

 

[330xi]

You can try it. I always have 2-3 sets of spare plugs with me at all times. I'd say replace 'em and do a few plug chops.

 

[Shane0524]

I'm going to try the plugs before anything just as a start. On a slightly different note, is there anything that would cause the carbs to not hold fuel and have the gas flow back to the tank when shut off? Thus creating a hard start because the carbs have to reprime themselves. That would also cause a rich oil start and maybe make the plugs look like they do.?

 

[soccerdad]

I'm going to try the plugs before anything just as a start. On a slightly different note, is there anything that would cause the carbs to not hold fuel and have the gas flow back to the tank when shut off? Thus creating a hard start because the carbs have to reprime themselves. That would also cause a rich oil start and maybe make the plugs look like they do.?

Not really. It is pretty much a one way system. It may seem like it is draining back, but I doubt it. I guess if the tank was not venting and somehow ending up with a vacuum in it. But this is not likely. I bet it is really flooding (leaking needle) and it takes a while to push that out before enough air gets in through the carbs to start it.

 

[Shane0524]

I just don't know how the needles and seats could be leaking considering they are brand new with correct 1.5 size from sbt and pop off pressure set correctly using old springs and arms. The machine ran fine before my rebuild I just did the rebuild because of the ageing rubber parts, but now it runs the same once started just a little hard to start after sitting for more that a minute or so .

 

[racerxxx]

Unfortunately, it very well could be the aftermarket parts

Just a quick sampling, a quick read and you'll get the gist.

http://www.seadooforum.com/showthread.php?33146-Flooding-Out-after-Carb-Rebuild
http://www.seadooforum.com/showthread.php?59721-Mikuni-Carb-Rebuild-Kits
http://www.seadooforum.com/showthread.php?27478-Carb-Rebuild-Kits-OEM-Mikuni-or-other
http://www.seadooforum.com/showthread.php?18073-Carb-Rebuild-with-SBT

 

[1983]

Plugs are cheap. Keep sets gapped and ready to go.

As I've said with all these carb discussions/threads. Bleed down psi test is just as important as pop off. Really read the tutorials on what these mikunis do then you will understand what these carbs are doing during operation on ski.

Rob

 

[purple_people_eater]

I used SBT kits.

this is your issue my friend. i never use any part sbt makes. i've rebuilt several sets of carbs where sbt kits where used by the owner and they come into my shop or call me saying "i just rebuilt the carbs, why am i still having fuel issues?"

i always ask if mikuni kits, needles and seats where used, 75% of the time the answer is no, the other 25% are still running grey fuel lines.

 

[AdamXP800]

I wouldn't say that all SBT parts are junk, but the carb kits are a waste of money.



96 XP800!
Keep the 2 strokes alive!

 

[Shane0524]

Ok so I'm probably going to have to replace the needle and seat as well as the round rubber diaphragm, right? (with genuine mikuni parts) where is the best source for genuine mikuni parts? (Parker yamaha )?