175 2 stroke wont rev past 2k

[gohawks688]

Symptom persisted today on a test run. Components would have been cool to start test run. So I don't think it's a issue.
If it's not spark what else could cause my symptoms? Could the advance module be limiting timing?

 

[gohawks688]

Cleaned carbs. Spotless inside. So that doesn't seem to be the issue.
Will be checking idle and timing advance next.

 

[gohawks688]

Checked timing today in garage.
While cranking engine 9 def atdc
While cranking with throttle advanced 19 btdcthis is with white wire to spark box disconnect. Didn't seem to change when I plugged it back in?
Also checked spark again with my new cdi adjustable tester. 3/8 blue spark all day long.
I'm at a loss guys

 

[Dukedog]

chunk tha "idle speed controller" (what ya call spark advance box) in tha trash... re do timing...
after ya throw it away make sure ya have a white/black "jumper" (length is a non issue) between tha bias post on both switch boxes....

 

[BrianVT]

You didn't mention checking some of the simple stuff.
Check fuel filter(s), check the condition of the inside the fuel lines, and check the ball valve at the quick connector.
The inside of my fuel lines was degrading. There was a clear inner liner that was falling apart. I noticed a bit of it in the fuel filter that I replaced. A bunch of this crap built up ahead of my ball valve and restricted fuel flow. The gray fuel line is known for this.
I had the same symptoms you are experiencing. I cleaned out the connector and replaced the fuel lines. All good now.
I hope your solution is this simple/cheap.

 

[gohawks688]

chunk tha "idle speed controller" (what ya call spark advance box) in tha trash... re do timing...
after ya throw it away make sure ya have a white/black "jumper" (length is a non issue) between tha bias post on both switch boxes....

i have been considering doing this. what should i set timing after the box is removed? stick with the standard 0-9 ATDC at idle and max 20 BTDC?

 

[gohawks688]

You didn't mention checking some of the simple stuff.
Check fuel filter(s), check the condition of the inside the fuel lines, and check the ball valve at the quick connector.
The inside of my fuel lines was degrading. There was a clear inner liner that was falling apart. I noticed a bit of it in the fuel filter that I replaced. A bunch of this crap built up ahead of my ball valve and restricted fuel flow. The gray fuel line is known for this.
I had the same symptoms you are experiencing. I cleaned out the connector and replaced the fuel lines. All good now.
I hope your solution is this simple/cheap.

I checked most of those things when I initially ran into this problem. switch boxes was the problem then so I struggle to think its fuel now. I do have the grey lines too. I will check the qd for build up, had this happen on a kicker before only found that by luck.
earlier this season:
new fuel pump
removed filter after fuel pump (it seemed to restrict flow) have large fuel water separator/filter before fuel pump. thats new this season, guess i should check that again.

 

[gohawks688]

Could it be stator high speed winding? Just because it has good spark at idle doesn't mean it has good spark at RPM. is there anything else that can cause bad spark at RPM?
I checked resistance on the stator windings earlier this year and they were in spec but I guess I should check again.

 

[Dukedog]

correct on tha stator.. it can even check good with jus a resistance number but actually be "not good"... a bad high side most times a motor will perform normal in all aspects till ya get ta 2500/3000 rpm.. it will still be smooth but jus won't accelerate...
timin' after ya chunk tha module?.. idle has no set number.. set it in tha driveway where it starts and idles smooth when left alone.. rpm doesn't mater.. after you get everything done to where ya satisfied all is good take it to tha lake.. in tha water, in gear set idle timin' only to whatever speed/rpm makes both you and tha motor happy.. number has no bearin'..
total timin'.. set at no more tha 23*... run good fuel only........

 

[gohawks688]

correct on tha stator.. it can even check good with jus a resistance number but actually be "not good"... a bad high side most times a motor will perform normal in all aspects till ya get ta 2500/3000 rpm.. it will still be smooth but jus won't accelerate...
timin' after ya chunk tha module?.. idle has no set number.. set it in tha driveway where it starts and idles smooth when left alone.. rpm doesn't mater.. after you get everything done to where ya satisfied all is good take it to tha lake.. in tha water, in gear set idle timin' only to whatever speed/rpm makes both you and tha motor happy.. number has no bearin'..
total timin'.. set at no more tha 23*... run good fuel only........

I will check the stator high speed later this week. I have a DVA but I have been having trouble getting it to work with my multi meter. Need to get that figured out

Would an intermittent stator high speed toast a switch box? Wondering if that is why my switch box went out originally and a replacement solved the problem but now it is back.

 

[Dukedog]

i've never had one do it but think i've heard they could possibly.. never change one switch box one at a time.. always both.. a bad bias on one can mask a problem with it and/or cause a good one ta goo bad.....

 

[gohawks688]

i've never had one do it but think i've heard they could possibly.. never change one switch box one at a time.. always both.. a bad bias on one can mask a problem with it and/or cause a good one ta goo bad..

I changed both. seems weird I am now having the same issue with the low max rpm but have spark on all cylinders (i changed boxes because I only had spark on one bank)

 

[gohawks688]

I will check the stator high speed later this week. I have a DVA but I have been having trouble getting it to work with my multi meter. Need to get that figured out

Would an intermittent stator high speed toast a switch box? Wondering if that is why my switch box went out originally and a replacement solved the problem but now it is back.

Ok guys here's the results following stator dva at cranking speed.
Per manual Stator high speed (red wire) 400 rpm 25-50 volts
With spark advance box plugged in 3.x volts
Without spark advance box plugged in 17 volts
Both of these are below spec one obviously more than the other. So here's my question... Is the stator bad (only 8 Volts off tho that's roughly 30 percent) or is the idle box what's really causing me my problems. I'm leaning towards a water test with the idle box removed before I go after replacing the stator.
Note I did the test at cranking . I didn't want to drag the boat into the driveway to test , with the really bad values with idle box plugged in I don't know if it's necessary to test at other speeds. Will proby jump right to water test without box.

 

[gohawks688]

Water test results
Outer box 1000rpm
Low speed 212
High speed 130
Inner box
High speed 125-130
Low speed 213
Bias 5.5
All this seems to be in spec. I can't get it to 3000 rpm in gear and I don't want to rev in neutral to 3000 so that is all the info I have to go on.
I am unable to get voltage reading at the coil. One meter shuts off when I attempt to read the coil voltage and the other is so sporadic that I can't read it. Both these meters read the other dva tests just fine. Any one know what's going on here?

So ignition seems fine. I'm at a loss. Going to rebuild the fuel pump again just to cross that off the list.

 

[BrianVT]

Have you checked for deteriorating fuel lines and debris obstructing the ball valve at the quick connector?

 

[gohawks688]

Have you checked for deteriorating fuel lines and debris obstructing the ball valve at the quick connector?

I have spot checked the connectors and fuel lines (they are the grey kind). No deterioration or debris found in the lines are filters.
I am buying a section of clear fuel line on the way home to install to check for air bubbles to hopefully rule that out for good.

Drained the big fuel filter. I have it sitting in a jar to see if there is any water that separates out.

 

[gohawks688]

Does anyone know why both my meters/DVA wig out when i try to measure coil voltage? one shuts off the other moves so fast i cant read the numbers.

 

[gohawks688]

Put clear line between fuel pump and carburetor. Looks good very few air bubbles on initial start. Then after one minute zero air bubbles.

 

[gohawks688]

Put clear line between fuel pump and carburetor. Looks good very few air bubbles on initial start. Then after one minute zero air bubbles.

Spent some time adjusting idle mixture screws. Started at 2 turns out then went in until idle got worse then backed out 1/2 turn from there.

Bottom two mixture screws did not effect idle even when screwed all the way in.... Verified once again had blue spark jumping 3/8 to 1/2 inch on tester.... Compression verified earlier in the process at 115 to 120. Carbs cleaned one week ago. Am I on the right track to finding my issue? Remember that this problem cam on suddenly when underway.

What would cause cylinders not to fire when they have spark and compression and I assume fuel. Idle doesn't seem to change when bottom two cylinders are running on the spark tester vs actually sparking.

Do reeds effect compression?

 

[BrianVT]

"...and I assume fuel."
You still haven't confirmed no blockage at the quick connector ball valve.
Would take 15 minutes including cleaning if needed.
If you don't want to check then I'll move on.