XR6 150 Cylinder Question?

[BassHole559]

I’m having the common momentary hesitation on rapid throttle advance but smooths out. Sometimes if I let it sit in idle for about a minute then gun it, it Boggs down and dies. Motor isles fine. It’s a 2002 XR6 150 S/N 0T591137 I timed the motor using the upper starboard spark wire as that’s what my manual calls my “no.1” cylinder to specs. Did the link, sync, still momentary hesitation. I’ve changed, bulb, all fuel hoses, fuel pump, both fuel filters, verified Thermal relief valve operates, checked all bleed check valves and replaced all hoses, inspected reeds, replaced all gaskets, thoroughly cleaned carbs, adjusted floats, etc. compression was solid at 115-118 psi. I Tested my entire ignition and charge system. Replaced my entire cooling system. Everything is good. I even took my seats out to look at my fuel tank and see if it was venting properly. After all this I did timing and sync once more to make sure. So I’m confident it’s all down to fuel air mixture. Fresh 87 octane non ethanol with stabilizer was used.

I got the manual for the WM carbs and I’m confused about a couple things. On their diagram, it says the TOP PORT barrel is the No.1 cylinder on one of their diagrams. PIC is below post. Before someone says I’m looking at it wrong, the sync link lever is key. I thought for sure I was looking at it wrong until I saw that. Not a big deal if the jets were all the same size, but that’s not the case. So, is it possible the different size jets are on the wrong side of the carbs and that’s causing my Issues?

Second question, idle air mix screws, manuals say these things should be adjusted evenly 1 1/2 +\- 1/8 turn. There is no way to hook up a vacuum gage to tune these guys and adjusting them Evenly makes no sense if a couple of the jets are different sizes. Right now all my needles are turned out 1 5/8 turn. Less than that the problem gets worse. More, than that worse.

im stumped but determined to get this problem fixed. Please advise. Thank you in advance.

 

[Dukedog]

I got the manual for the WM carbs and I’m confused about a couple things. On their diagram, it says the TOP PORT barrel is the No.1 cylinder on one of their diagrams. PIC is below post. Before someone says I’m looking at it wrong, the sync link lever is key. I thought for sure I was looking at it wrong until I saw that. Not a big deal if the jets were all the same size, but that’s not the case. So, is it possible the different size jets are on the wrong side of the carbs and that’s causing my Issues?


Second question, idle air mix screws, manuals say these things should be adjusted evenly 1 1/2 +\- 1/8 turn. There is no way to hook up a vacuum gage to tune these guys and adjusting them Evenly makes no sense if a couple of the jets are different sizes. Right now all my needles are turned out 1 5/8 turn. Less than that the problem gets worse. More, than that worse.

im stumped but determined to get this problem fixed. Please advise. Thank you in advance.

no,to first ?..

jetting is not tha problem unless someone has been in there foolin' with 'em.. ​

you should have wmv 16's?.. correct?

first, forget "book" idle timing numbers.. set idle timing with boat in tha water, in gear to what ever makes you and tha motor happy... when doin' L&S make sure you have a tiny "gap" between throttle cam and roller of carb linkage.. this lets tha advance arm move a fraction before throttle plates.. sounds like ya close enough on "tweakin'" fine tune screws...

have you had tha carburetors apart?

 

[BassHole559]

I did have the carbs apart. I actually have a machinist drill bit set so I mic’ed out the jets holes and they are correct factory size and in the right spots according to the Merc manual. I’m unsure about them being -16’s. I bought it used and assume their stock ones. I’ll check today. One thing I didn’t see in the manual was the gap you mentioned on the cam. Which makes a lot of sense because I was thinking my butterflies were opening too quick causing a flameout condition. Thanks man. I could be grasping at straws here over a minor hesitation issue because otherwise it screams for a 150. I just like things working optimally. Thanks again!

 

[Dukedog]

one thing that is essential.. when ever they are taken apart is almost a must to use "new" gaskets inside and out.. no mater what they look like.. once "crushed" they have a sad chance of sealin' properly tha second time...

yeah, tha "gap" thing is something we use on tha "hot rods".. some of which go as far as 3/8 ta 1/2"..... some are "locked in" at 25* from tha get go...………..

 

[BassHole559]

Wow, that far of a gap between the roller and cam seems more than what I was thinking! I hear you about the carb gaskets. I did have to reuse them once making float adjustments but, they aren’t leaking and I didn’t wrench them down.

This might sound ghetto, but I soaked the carb float gasket in soapy warm water for 30 minutes cause they are the paper type then let them dry. My theory was that water would make them expand out a little and allow them to re compress. Seemed to work for now. I’ll put more on order once I get it all tuned up but who can afford those expensive buggers just to make float adjustments. Had to take them off a couple times to get floats right and only bought two sets.

Learned information... floats should not be set flush with bowl. Best at 5/32 to 3/16 lower than flush. Atleast for mine anyways.

Last question... maybe... lol. I don’t see any movement on my throttle arm when going from “dead idle” to in gear idle. To me it seems like “in gear” idle should make-up the difference up in roller gap with maybe a slight opening of the butterflies. I’m not an expert though and anything I have learned about my motor has come from experimentation with different settings, blindly replacing sh@$, and my experience as an aviation mechanic. Which btw, modern planes don’t have 2 strokes.

 

[Dukedog]

two cables, two movements.. throttle/advance arm should not move till throttle cable is engaged at shifter... even "in gear" at idle.. that's why idle timing has/should be only control of motor rpm "at idle"..

 

[BassHole559]

Copy all. Thanks so much for your guidance. I’ll report back if this is a fix or not.

 

[BassHole559]

I’m convinced my powerhead is shot. I tried every possible adjustment to get the fuel air right. I think that compression gage from autozone I used wasn’t right. Before my issue started my idle mix needles didn’t need adjusted past 1 1/4 to run like a demon. Now they have to be out further and I lose power on fast acceleration. Something is leaking internally. I’m gonna attempt to rebuild the motor myself with a kit after I disassemble and take it to a machine shop to get trued up.

Unless anyone has any other ideas. If not, can anyone recommend a good kit to do the rebuild with?

 

[Dukedog]

might try all new carb gaskets, settin' floats by tha book one more time.. comp won't produce problem ya havin'....jmo...gl whichever way ya go.

 

[racerone]

Pull heads off and inspect cylinder walls.

 

[BassHole559]

I’ll pull head tomorrow and check it out. If I don’t see anything wrong then I will also try new gaskets on carbs, and try setting float level according to manual but I did do that when I rebuilt them and one of the carbs wouldn’t stop fuel when full. But i’ll give it another go before I say screw it and rebuild. Atleast if rebuilding doesn’t work I will have a new powerhead once I do figure it out. Thanks again for all your suggestions.

 

[Dukedog]

one outta three should tell ya something is amiss in it....

 

[BassHole559]

Floats adjusted, gaskets replaced same symptoms. Before I pull the head for this bogging issue, cause your right, I don’t think compression is the problem, how likely do you think I have an ignition problem. I could have missed something. Maybe a high speed misfire? I remember resistance on the trigger coil being in spec but would jump around when I moved the timing tree quickly forward and aft then stabilize in spec. Slow movements would stay relatively same ohms. I’m gonna redo the compression test in the mean time it takes someone to respond.

 

[Dukedog]

still have one carb pushin' fuel past needle and seat?.. control module check out?.. 'bout empty as far doing' this ona computer.. hard to do without being able not touch/hear it....

 

[BassHole559]

Float seems to be shutting off the fuel. I ohm’ed out and diode checked all six CDM’s, ohmed stator and trigger. Also have 220 peak volts AC coming off stator while cranking on green and white wire, 158 vac RMS. Nothing out of limits other than stated above but I think that’s normal for a coil to glitch the meter on a rapid ohm change. Re-verified voltage rectifiers are putting out 14.5 VDC to battery charging circuit. My tach also works so I think their good. Started pouring rain so I couldn’t do another compression check. Think I’m gonna harbor freight it up and get their leak down tester. Probably not the most accurate but should give me some more info before I pull the head.

Only thing I cant seem to find data on to read out is the the actual module (switch box). Anyone have gouge on that?

Thanks again duke. Just bouncing ideas off you helps me strategize next move. All I wanna do is get back to fishing. I owe ya a beer or 12. If your ever in Maryland hit me up. John.d.valentine@outlook.com. I’ll be stationed there for the next 3 years.

 

[Dukedog]

only other thing I can think of is go to a large gap between roller and cam.. at least 1/2".. a "semi bad" trigger will sometimes show its true colors doin' this....

 

[BassHole559]

Bought me a gage, performed compression test. Findings: 1= 94, 3= 96, 5= 96, 2= 92, 4= 92, 6= 92. This time I verified my gage was dead on with a calibrated reg. So, autozone gages before were likely bad. I read these results as a normally worn engine. Not a single or pair of cylinders stand out. Seems on par for it’s age but I don’t know how many hours it actually has. Isles fine. At this point, is it worth doing a leak-down test? I feel like it just needs rebuilt. I don’t wanna use it til it blows cause then the power head would likely be useless and I can’t afford a new or decent used motor right now. I can afford about 1,500 in a for a kit, and heads machined. Thoughts?

 

[BassHole559]

Duke, I think I figured it out. Called a mechanic about a rebuild kit. Told him my numbers. He asked if I decarbed it recently. He said sometimes doing that can lower the numbers and I shouldn’t worry and something else is likely causing it like you said. So I got to looking at the only system I haven’t really looked at. The oil injection. Took plugs off that I recently changed about 25 hours ago and they were fouled. More oil than I’m used to seeing in there. So, I think the gas is too rich at idle causing misfires from plug fouling. Cleaned plugs with brake cleaner, put carbs idle jets at 1 3/8 out from 1 3/4. Started right up on first choke/crank and idled fine. Went to 1 1/2 out on idle jets, no hesitation. Now I have to figure out why my oil injection system is Wonkey. Concur?

 

[BassHole559]

Duke, I think I figured it out. Called a mechanic about a rebuild kit. Told him my numbers. He asked if I decarbed it recently. He said sometimes doing that can lower the numbers and I shouldn’t worry and something else is likely causing it like you said. So I got to looking at the only system I haven’t really looked at. The oil injection. Took plugs off that I recently changed about 25 hours ago and they were fouled. More oil than I’m used to seeing in there. So, I think the gas is too rich at idle causing misfires from plug fouling. Cleaned plugs with brake cleaner, put carbs idle jets at 1 3/8 out from 1 3/4. Started right up on first choke/crank and idled fine. Went to 1 1/2 out on idle jets, no hesitation. Now I have to figure out why my oil injection system is Wonkey. I thought black oily plugs were normal for a 2 stroke. Concur?

 

[Dukedog]

you haven't mentioned what its on?.. how you use it?.. how its set up?..

no, it should not fowl plugs at anytime or be "oily" at any time.. maybe a "little wet"... plugs should last a very long time...

comp numbers should be 110 or better ina "normal" way with known good gauge.. it has relief slots that show up at crankin' speed comp test... low comp like you say will show up as motor being slow to respond, labor a tad at any throttle applied.. usually not noticed over time till it gets really bad.... your comp numbers?.. never applied tha way you came up with those?.

no a fan of tha "way" some do the "de-carb" thing.. but a tab bit of "quik-klean" or sea foam ever so often seems ta work but mine always taken apart and looked at way more than normal boat guys!

sounds like your under control and headed in tha right direction with it.....