So i have a 701 motor(62T Raider, dual 38s) that I am trying to get running in my old VXR. I can get it to start and idle great, low speed is dialed in well. Doesn't want to rev past 4800-5000 rpm. Seems like its too rich but everything is set to stock values on the carbs and ign timing. Compression is on the low side(120) but even across the holes. I am trying to run a 61x head and manifold with breadbox stock exhaust. Will a 62T run like this or do I need at least the stock raider/blaster chamber? I have a garage full of 650/701 motor parts but no raider exhausts. Trying not to drop a bunch of money in an old couch so a $700 used pipe is out of the question, at least for this ski. Any suggestions would be appreciated.
Exhaust Question
- Thread starter killpop
- Start date
Thanks for the prompt response. Thats kinda what I was thinking, not expecting full output but at least to run decently. I must have other problems somewhere. its just odd that the more I lean out they high speed screws, the better it runs (more RPMs and smoother). Starting from the settings from the manual, going richer makes it worse and leaner to the point where they are all the way in shows a lot of improvement. Of course I am terrified to run it like this for any length of time. Also, it only does this when the trailer is in the water, when dry it will rev to almost 7k. Would it be worth tying to down jet it or would that be too dangerous?
I verified that they have what came in them stock, 120 (f) 130(r) for the high and lows looked to be the 67.5 but i couldn't actually read the number on the low. Carbs also have the correct stamp, 62T01F and 62T01R. I don't think its relevant but I have not been able to accurately measure the pop off pressures, my cobbled together gauge only goes to 30psi and they seem to be a little above that. I have read conflicting info on what they should be. I am curious what other people end up with whey start swapping jet sizes on a custom build.
I've got nothin. My experience is that just about anything will be pretty close with stock jetting in stock 38mm carbs, but never tried anything like what you're doing.
Stock popoff is usually really high, 50 ish (I don't remember the exact number), so that all seems reasonable.
I would probably use the "stock" jetting from a superjet rather than the "stock" from the couch you got the 62t from, but either way it's not hugely different than what you have.
one thing to check is make sure the little o ring n the needle seat isn't leaking. Basically if it has some resistance to pull the seat out and doesn't leak when you're checking popoff it should be good.
bored&stroked
Urban redneck
- Location
- AZ
Check superjet jetting and match it. If it already matches, then no idea.
- Location
- Illinois
So you have the high speed fuel screws basically turned all the way in at this point? If not, lean it out.
I never dwell on jetting specs. Just give it what it needs.
I never dwell on jetting specs. Just give it what it needs.
I guess thats kinda what I'm wondering, how common is it to end up that far away from the book specs? It's entirely possible that diagnosis of it been overly rich could be wrong. I'll try to take a video in the next couple of days, maybe that will be of some help. With the screws all the way in, does that mean that its getting no fuel in their effective range or are they additive to the HS jet? Looking through the SBN manual, this isn't entirely clear.
High speed screw and jet are additive, so turning them all the way in is not cutting off all of the fuel. You have a pretty big difference between the two high speed jets, it's possible that one is rich and the other is lean. I would go 130 on both, then use the screws to get a direction. If I'm not sure which direction to go I always go richer.
I checked the n/s during the pop off test, both good though I didn't think to look to see what size they were. Was a stock 650 in the ski before, ran really well. I was recently given 2 701 motors, a 61X and a 62T. I put in the 62T cuz I thought, if having 1 carb was good, having 2 carbs must be better, right? Wish I had waited till the winter to start messing with it instead of wasting half the ride season. I have another 650 ski (VXR) that runs perfect that I have been swapping electrical parts back and forth with, problem never follows to other ski. Might a bad set of reeds make a motor act this way? I glanced at them before I installed but not very closely. At this point, it has to be something simple that I have overlooked but I am running out of ideas.
My first idea to tune the ski failed. I built an EGT reader out of an Arduino and a couple of thermocouples, too bad it shuts down if its too close to the ski while the engine in running. Electromagnetic interference from the ign is just too much for it.
My first idea to tune the ski failed. I built an EGT reader out of an Arduino and a couple of thermocouples, too bad it shuts down if its too close to the ski while the engine in running. Electromagnetic interference from the ign is just too much for it.
Last edited:
- Location
- Granbury, TX
It could definitely be bad reeds. I had a customer bring his ski back to me recently. I rebuilt it 7 years ago ('01 GP1200r). It had sat for 5 years and needed a complete fuel system refresh. I ultrasonic cleaned the carbs, replaced all fuel lines, rebuilt the carbs with mikuni oem kits and a whole lot of other stuff. I bore scoped the reeds as I didn't want to break the intake manifold seal and have to pressure test the motor again. It started and idled GREAT. Once on the water it wouldn't rev past about 4000-4800 rpm and sounded burbly rich, just like yours. After checking and testing everything I could think of and 5 trips to the lake, I finally bit the bullet and pulled the intake and reeds. They were trashed. I think they looked fine until I ran the motor and they fell apart. Installed new reeds and the ski ran like a scalded dog. ALWAYS check your reeds.
After taking the video and watching it a few times, I'm also more leaning towards reed valves. I have never had to replace a set that wasn't obviously broken. I have had my 2 650 VXRs for 12 years and they are still on the set that they came with. While recording, I was trying to keep the throttle shaft in view so I could later map out where in the range I was having the issue but the oil line keep getting in the way.
So what do you guys think, carb issue or reed valves or something completely different?
btw, make sure your volume is turned down, it gets loud real quick
So what do you guys think, carb issue or reed valves or something completely different?
btw, make sure your volume is turned down, it gets loud real quick
- Location
- Granbury, TX
Dude. Reeds. You're shooting fuel/air mix out the carbs. Pull the intake.
so I take it that this is a common failure mode for reeds? My 650s have done this sort of thing when my fuel returns have gotten plugged up. Maybe didn't spit up as much but you could definitely feel it on your hands. Also had a waterbox go bad and randomly plug up and it would do this right before the ski died. Pulling intake tonight. But man, I hope thats it, I am tired of messing with this thing.
- Location
- Irish Hills, MI
personally id use a small inspection mirror once the carbs are off, before id pull intake.
- Location
- Irish Hills, MI
youll be be able to see if reed is resting correctly on cage or damaged/missing/bent ect. of the reed.
I donno, they look ok to me. No gaps as they rest and when you twang each pedal with your fingernail, they all make the same crisp sharp sound. I guess I will replace them anyway as I have already ordered some and I think this is the only engine I have that they will fit.
How do they look to you guys? Is there any other kind of test I can run on them? I can get better pics of them, I know that the light situation in my shop is less than ideal.
How do they look to you guys? Is there any other kind of test I can run on them? I can get better pics of them, I know that the light situation in my shop is less than ideal.
