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Old 11-23-2006, 04:34 PM   #1 (permalink)
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1978 SRX 440 Problems

Yeah my dad has a srx within a few years of that range it is that or a 79 i believe. Anyways, it just runs like crap. We have replaced some things in the clutch and all the fuel line along with the coils, cleaned the carbs. It has a problem with bogging down. Everytime you give it throttle it bogs way down and has like nothing. You have to play with it in order to get it to go a little bit. Its a fast sled i know that and it dont have too many miles on it, maybe like a lttle less then 2000. Compression is good in each cylinder and we both have run out of ideas. Maybe someone else knows what it could be....
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Old 11-24-2006, 01:08 PM   #2 (permalink)
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I dont know much about that prticular sled but maybe try pulling fuel pump apart or make sure there is nothing pluging off lines in fuel tank. Maybe somthing plugging off exaust? I had a mouse in mine once. check reeds arnt sticking.
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Old 11-28-2006, 08:00 PM   #3 (permalink)
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it's the carbs...it is too rich on bottom end.
have you moved the needle clip position to lean it out a bit on bottom end?
the carbs are mikui powerjet carbs which means you can adjust the size of the main jets with a twist of the white dial on the bototm of the carbs.
raising the engagment will also help with bog issues.
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Old 11-28-2006, 11:03 PM   #4 (permalink)
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just curious do you raise or lower the needle to lean it out on the bottom end?
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Old 11-28-2006, 11:25 PM   #5 (permalink)
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the needle adjusts low to mid RPM range, it is lowered (raise clip) to lean fuel.

i had the same vintage SRX with those symptoms, my engine and fuel were fine, had to engage the sled around 5000-5200RPM to get rid of the bog. these were basically racing sleds, not really to good for trail use, i did take mine on one trail ride, was fun on the straights, wouldnt turn for crap!
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Old 12-01-2006, 08:42 PM   #6 (permalink)
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Quote:
Originally Posted by SSnthe10s
just curious do you raise or lower the needle to lean it out on the bottom end?
think about it for a sec.
you want to lower the needle in the needle jet to restrict fuel flow a bit more on bottom end. so raising the clip on the needle thus dropps the needle lower in the needle jet and restricts fuel delivery more down low.
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Old 12-02-2006, 03:05 PM   #7 (permalink)
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yea, thanks guys. i have a slight low end bog. ima raise that clip.
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Old 12-02-2006, 10:51 PM   #8 (permalink)
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I have actually recently had the same problem with my srx...but unfortunatly for me it's my crank...idles fine but then just bogs out and will just move about an inch jump at a time...if it even moves...
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Old 12-03-2006, 05:15 PM   #9 (permalink)
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what makes you think your crank is bad?
if the motor still runs, the crank must be ok. does it turn over smoothly with the plugs out?
what happens to a crank is usualy a bad bearing, broken crank piece or when you sieze the motor the flywheel pin turns (slips) and knocks your ignition timing off.
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Old 12-03-2006, 05:17 PM   #10 (permalink)
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a smaller (or larger) pilot jet can help with low end bog issues also.
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Old 12-03-2006, 05:20 PM   #11 (permalink)
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A sled will can still run with a bad crank....but if it does you won't get much effort out of it. With mine, I can slowly pull it over and atually watch the bolt on my clutch going off centre...Sister's bf is a local mechanic and he came and took a look at it and said it was the crank, and that he had the same issue with his 2004 pro xr 800, the sled ran, but wouldnt move...
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Old 12-03-2006, 06:12 PM   #12 (permalink)
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sounds like the crank twisted, hopefully you just need it phased back in and all the bearings and stuff are good.
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Old 12-04-2006, 01:52 PM   #13 (permalink)
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Bent the PTO stub possibly. Has the clutch been pulled and checked for proper installation?
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Old 12-04-2006, 04:31 PM   #14 (permalink)
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sounds like the bearings are shot. time for a crank rebuild.
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Old 12-04-2006, 05:24 PM   #15 (permalink)
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the more i think about it now. you may have a broken weight wheel on the crank.
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Old 12-04-2006, 07:50 PM   #16 (permalink)
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Ya Im gonna haul it apart now tomorrow....see if there is anything visible. rying to find the number or website to adrian bonnard in Quebec, he rebuilds cranks for a good price. Anyone know the number?
I may just look for a drop in 77 motor...you guys know or have any idea where I could get my hands on one?
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Old 12-05-2006, 02:29 AM   #17 (permalink)
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Old 12-05-2006, 10:23 AM   #18 (permalink)
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Atelier Adrien Bernard for cylinder and crankshaft rebuilding and replating in Quebec, Canada

i just purchased a rebuilt 78 srx crank from them. the cost was $230 with my broke crank as a core.
the problem with dropping in a 77 srx motor is the 77 srx's used a 18mm dia wrist pin piston which you can not get pistons for anymore. go with a rebuilt 78 crank with the 20mm dia wrist pin pistons as they are still readily available.
if you do pickup a 77 srx motor, make sure it has a 78 crank in it or atleast the 78 20mm wrist pin connecting rods.
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Old 12-05-2006, 01:34 PM   #19 (permalink)
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Thanks a million for the website, greatly appreciated. And thanks for letting me know about the wristpin diference, becuz i had no idea. $230? that sounds like a good deal to me, I was thinkin somewhere around the 600-700...thats great, and another plus is that im only 10 km's from the border of quebec so shipping shouldnt be a killer! I just need to get the srx up and running, races start soon
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Old 12-06-2006, 01:31 PM   #20 (permalink)
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Adrien Bernard has none... all they can do is fix mine. Know anywhere else where i can get a crank, snoepro? You seem like you know alot about the srx's of the early days!
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