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Hi! About a week ago my friend and I went in on a pair of 1994 yamaha vxr's (his was a vxr pro). When we bought them the guy struggled to turn them over but they eventually did and everything seemed descent accept the oil lines were busted and the hulls were filled with oil. We installed new fuel lines, fuel filters/water separators, spark plugs, and oil pump block off kits and went and ran them the other day. Mine idled like a pro and ran great at 1/2-3/4 throttle, but at full throttle it hesitated. I am trying to figure out what this was from. My guesses were either that the tab on the top of the intake needed to be open, I need to make carb adjustments (or maybe rebuild it), or maybe I am running the wrong mixture (50:1 but a little rich making it closer to 45:1). I don't think adjusting my high speed screw on the carb would change anything because i'm premixing. also, I don't think it's my mixture, because my friend ran the same mixture and he had no issues at top speed.

Also, my friend's struggled idling. We set the idle speed decently high but it still staled a lot. His ski is set up with all the same details i told you (new stuff w/ oil block and premix). Any thoughts on what a bad idle could be?

Sorry to ask so much, Thanks for your help!
 

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Jetjon,
Hi, welcome aboard.
I have 2 of vxr pro's. Nice little playful ski. I ride them frequently.
Have you checked your compression? Broken oil lines is your key. If it was run at all starving for oil, one or both cylinders got damaged. The more you run it the worse the damage gets. Compression on the 650/701 should be 140/150ish. If that checks out ok then I'd say carb.
If you don't already have one the Clymer manual is pretty good on those skis.
But most of all get the compression checked before you ride again.
 

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Discussion Starter #3
Hi! Thanks for your response. I just checked compression and my ski has 150psi in one cylinder and 149 in the other (not bad for a 24 year old engine!). My friend's ski had 148 and 144 which i think is nothing to worry about any time soon. The previous owner replaced the spark plug caps on my engine with cheap ones he bought at the lawnmower store. I'm pretty sure that's my problem so i will replace those and pray that it fixes my problem. I also will rebuild the carbs sometime soon because i don't want to risk running with bad carbs and damaging something. For getting new sparkplug caps, can I just buy any 20$ Yamaha OEM plug cap (nonspecific to any engine)? Or should I get the 40$ (each) ones from walmart? Or should I get the entire wire assembly for 100$? I want to be cheap, but I also want to do it the right the first time and only do it once.
 

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Both skis compression is great. Wouldn't worry on either.
As for plug boots go to Babbittsonline follow through oem parts, yr ext.... $47 apiece. but the true part for what you have.
When you go to order carb kits. get true mikuni kits. There a tad more expensive but worth every penny in long run. Also reuse old pop off/needle seat spring and document your high and low screw settings and put them back where they are. You'll be good to go. Below is a pic of my 2 vxr pro's 93/94 my cousin launching the 93. Also my GPr and cousins wave venture. IMG_20160705_140231760_1537875160793.jpg
 

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Fuel/oil mixture at 50/1 is fine. 45/1 gives you a bit of safety. Neither will effect carb settings as they adjust fuel/air mixture. So adjusting carb will affect runnability. For the hesitation try 1/4 turn in/out at a time on high screw. I would try out first. But wait till after carb rebuild. As rebuild may solve issue.
 

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Discussion Starter #6
We took the good spark plug boots off my friend's ski and tried it on mine and there was no performance difference. So i guess, although new boots were a necessity, it wasn't my problem. I get my parts in tomorrow and will rebuild the carb and replace the boots over the weekend. I let you know if it fixes my problem. Thanks for the help.
 

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Try trimming the wire back about 1/2 ", and rebulid the carb. Could be fuel pump related or just crap in the carb. The last 3/4 of throttle is the high speed screw. avg setting is around 7/8 - 1 turn out as a ball parkish figure. What do the plugs look like ?
 

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Discussion Starter #9
Plugs were new as of a week ago and I ran it twice. They were a little dark, but fine. Should I remove the spark plug wires and make sure theres no reistance through the entire wire when I replace the boots? or should I just cut it and not worry about it? I'm rebuilding the carbs tomorrow. I'll reset all the carb settings to stock and I'll let you know if that fixes it. Thanks for your responses.
 

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Really just sounds like the carbs need to be rebuilt, especially if they have been sitting, which it sounds like they were. You could just change the plug wires for the sake of doing it. They do eventually break down. Just go get some solid core wire and cut to fit.
 

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Discussion Starter #12
Yesterday we rebuilt our carbs and I replaced my plug boots. Both carbs seemed to have newer parts in them and everything was relatively in good shape accept mine had a gelatin like substance in the fuel pump side (probably from a previous owner running ethanol gas and letting it sit). Also, my popoff when I reused the spring was around 50psi when it should have been between 25-35psi. So I fixed all that and went to run it and my starter battery died. It only turned over twice while I was cranking it, and It didn't want to start when I pored gas in the top of the carb. I'll try again when my battery is recharged, but I think it should be a little happier right now. As for my friend's ski, it took a while to work fuel through the system and it needed some carb adjustments but it ran pretty good once we made adjustments (until he ran out of gas).
 

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Discussion Starter #14
My ski is still having some issues. I got it to crank and run and she idled like a champ. I took her to the lake to test and adjust carbs on the trailer and she ran like a pro until she didn't and then I couldn't get it to start, and then I got hit with heavy rain (figuritively and literally). I think it might be an electric issue and i might have a weak spark, but it might also be carb adjustments. I was wondering
1) Is the low speed screw the one that is closest to the back of the ski and on the left side of the carb when looking from the side of the ski that the carb is on. Also, is the high speed the one on the right?
2) I looked in manuals and they told me for the vxr pro 700, that the setting were something like Low:-5/8 High:-5/8-1 1/8 or something like that. This didn't work. We found on forums that it should be low:-2 and High: -1 1/2 (which still didn't work right, there is some other problem most likely), but that makes me wonder if the -1 1/8 for low and high that the manual tells me for the 650 is right or not. So.... What are the proper low and high speed adjustments for a 1994 Yamaha VXR 650? and for the 700? Do i trust the manual or people on threads? Thanks for the help.
 

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2 Turns out on low is to much for anything and you should be looking for another prob. like high pop off, bad fuel pump or lean low speed jetting.
1 1/8 low speed and 1-1 1/8 high should be good for the 650, and on the 700 I would start with 7/8 low and 1 high. Is the 700 a single or dual carb set up ?
Low speed screw controls starting and idle quality only. Pop off works with idle, off idle, up to about 1/4 throttle. Low speed jet up to 1/4 throttle, high speed jet 1/4-3/4 throttle, and high speed screw 3/4-full throttle.
Did it act like it ran out of gas or flooded ? Did you clean the tanks and change the inlet filters in the carbs ?
 

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Discussion Starter #16
Both are single carbs. Popoff on the 650 was set to 32psi and the 700 was set to 35psi. And yes, we cleaned the fuel tanks, replaced every fuel line (accept for vent because we ran out of line), replaced the fuel filter/water separator, and rebuilt everything in the carbs accept kept the jets and needles and seats because they were all good. The 700 did have scoring in the carb where someone ground out a channel on some screws because they stripped them (it looks like they took a dremel and cut a line through the screw and it also cut the body) I don't know if that makes any difference in performance. I think the 650 was acting like it was flooding. Both died off at 1/2 throttle or so when tested on the trailer in the water, but we could never find carb adjustments that worked right (we tried manual and what the forums said).
 

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Try this also. There is a restriction orifice in the pump cover for the return line. Make sure it is clear, but don't enlarge it any. Have you looked at the plugs since running ? If the pop off and low speed jets are set good, it will start almost instantly and idle smooth. Proper way to set the low speed screw is find the highest smooth idle then about 1/16 more out.
 

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Discussion Starter #18
Plugs on the 650 are light brown. Plugs on the 700 are kinda black. I think that's just from extensive testing and running on the wrong carb setting while trying to find the right setting. Ill take a look at the restriction orifice when I get a chance. Thanks for your responses!
 

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New Problems... I've had trouble getting the 650 started, it cranks for days but never turns over. I sanded down all my wire connections and everything and got it to turn over and run so i ran it for 5-10 seconds and turned it off. I let it sit and cool down then started it again and it ran perfect and started right up (yet again i only ran it for 5-10 seconds). Then I turned it off, screwed in the hose (without turning the hose on) and went to start it again and it just cranked. So i dug through my wires and sanded my grounds and got it to start when it wasn't connected to the hose, then ran it twice, then hooked up the hose, and it didn't start again. This has happened to me maybe 4 times now. Any idea why when I hook up the hose without the hose even on it only cranks?
 
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