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97 Challenging err, I mean Challenger...

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bflowers1971

bflowers1971

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So I bought this 97 Challenger and worked through some diagnosis of a no start situation. Turns out the starboard motor had a chipped piston on the PTO side. I figured this was due to fuel starvation so Ima rebuild the carbs and top end. I am wondering what size bore I should get, I know 1mm over would do the trick but if I can get away with .25, I'd rather do that (I think). Any advice on that would be appreciated. Also, I've ordered a replacement head since the old one looks quite pitted up from debris banging around in the cylinder. 1466955107313.jpg1466955102268.jpg1466955115945.jpg
 
Be sure to check the crank bearings while you have it in pieces. You need to measure the existing bore to know what pistons to go with. The machine shop I use said to get pistons first so he can measure them before boring. I don't know the maximum bore size on the jugs.
 
Well, I just got the jugs off and carbs rebuilt. Off to the machine shop next week for a .5mm over bore. With lots of luck, this thing should be going back together next weekend.
 
Ok, so the first machine shop held onto the cylinder jugs for a month before letting me know they couldn't bore them. Off to another machine shop who did a great job but one cylinder still had scoring on the walls so I had to order. 75 over pistons to get it done. Got that motor back together this past weekend and it sounds great. Now to rebuild the port engine carbs and put a new starter on it and it's off to the lake (hopefully)
 
I got 2 DENSO brand starter for $400 shipped. Shop around. Not a steal, but hopefully last 10+ years like OEM did.
 
Well, back to the drawing board. At least both motors start and run but they don'r run well. The starboard motor (the one I rebuilt the top end on) surges and struggles to build RPM and the port motor starts and runs smoother but will not build RPM. I set the carbs to one turn out on the low speed circuit and one and a half on the high speed circuit. After putting it in the water and running it, I turned the low speed adjusters in all the way to see if it made a difference to see what direction to go in. The starboard side then struggled to start and I think it fuel fouled the plugs but it made very little difference to the port side. I think I'm going to swap the carbs around to see if the problems follow the carbs and go from there. One issue I have is that the previous owner installed primer bulbs and the oil injection system was disabled so I fixed the injection system and am confident that it works. I feel like I need to get the fuel system to stock before trying to diagnose an issue. It looks like this will be a long road....
 
Did you use genuine Mikuni carb rebuild parts? VERY important as I found out first hand that even the stupid tiny thin plastic check valves were too thick on the ebay kit making the boat fall flat on it's face. It's expensive but worth it for the Genuine Mikuni parts. OSDparts has the best kits and deals.

Your high speed screws should be all completely shut on it (0 turns out). That is stock settings and you shouldn't really have to deviate from stock settings. the low speeds should be at 1 1/2 turns out plus or minus 1/4. Set them at 1 1/2 and I'm sure they will be fine.

Also make sure your jets are correct:
Main jet: Mag: 142.5 PTO: 145
Pilot jet: 67.5 for all

Also make sure to have the flame arrestor on while testing as it is needed to create the suction required to pull the fuel through. At least put the flame arrestors on with the metal frame that holds it in and leave the airbox off so you can get at stuff.
 
Great advise! I did not use the genuine Mikuni kits (my mistake). I also did not replace the needle and seat. Thanks again!
 
bflowers1971 said:
Great advise! I did not use the genuine Mikuni kits (my mistake). I also did not replace the needle and seat. Thanks again!
Click to expand...

I am sorry I did no ask this sooner... These carbs MUST have OEM kits as well as needle and seats. They aftermarket kits simply are not built up to specs. Wait until you see the difference when you put the kits next to each other.

There is no sense in doing anything else until the carbs are rebuilt again...
 
So I finally got the carbs rebuilt with Mikuni parts and the port engine starts right up and seems to have good throttle response. The stbd engine will not start. Since it sat all winter, the crank case filled up with oil (leaking crank seal). I pulled the plugs and blew all the oil out but still no start. When I check spark, there is a visible spark. I feel like it's probably not a fuel issue since the other engine fires right up and I rebuilt the carbs at the same time and in the same way. I also swapped the ignition coil from the running motor to the non running motor with no difference. I am scratching my head on this one since I have compression (checked it last week 130 each), fuel (I can see and smell it on the towel I put over the spark plug hole when blowing the oil out) and I have spark. To the best of my knowledge, this motor should run. Anything I am missing or should check?
 
It wss too rich, I guess from turning it over so much to get oil out of the crankcase, it was adding fuel. I pinched off the fuel line and cranked it a bunch and POW!
 
So I took her to the lake today after cleaning out a pretty substantial amount of fuel from the cylinder. It qould start if I pinch off the fuel line out of water only. I rebuilt all 4 carbs with Mikuni kits and the other engine runs like a champ. I think there is some kind of internal issue inside the carbs that is not addressed with thw rebuild kit. Time to swap the carbs to verify.
 
Yup, I swapped PTO carbs and now the poorly starting/running engine starts up fine. I think somewhere along the line, someone over tightened the HS adjuster and the valve body had a different hold down screw (not flush with valve body like the other carbs had. I'm not sure if either of these issues are causing my problem. It also pops off at 10 psi and wont hold more than 15 psi once i adjust pop off ( I can pump and pump but it bleeds air out somewhere). Any ideas if this carb needs replaced or can it be fixed?
 
I FOUND IT!!!!! Once I pulled the bad carb off and began monkeying around with it, I found it leaking from the pump side. There's an o ring that was flat in one spot. It just so happened that I had a different o ring that held and BAM!!! Both engines fire up, idle and have good response!!! I am so freekin' happy right now!!!!!
 
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cool, I also am new to forum and just got the exact same boat as you have. Starboard engine is locked, can't turn at driveshaft but will soak it in PB blaster overnight and hope it frees up. Bought at auction so unknown previous history/maintenance
 
mobilefleet said:
cool, I also am new to forum and just got the exact same boat as you have. Starboard engine is locked, can't turn at driveshaft but will soak it in PB blaster overnight and hope it frees up. Bought at auction so unknown previous history/maintenance
Click to expand...

you have to distinguish whether pump or motor
 
Well, took it out today and both motors started wit ease in the water but wouldn't get over 3500 to 4000 rpm. Brought her home to discover neutral safety switch working but fuel leaks from the pulse line (on both motors). Back out to the lake to verify the issue. Will it ever end?
 
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