For fun I thought I'd rebuild/restore on old bike. So I picked up an old 1978 KE175. I finally got it all together and running. I rebuilt the carbs, new rings, and top end gaskets. The bike will start on the first or second kick, and it will idle all day. In neutral, at a standstill, it will rev to redline (about 8,000rpm) at WOT. But once I'm moving, it will barely rev past 6,000rpm at WOT, it feels very sluggish, and barely picks up any speed. I'm still using the old, original plug (not sure the mileage on it), and it's getting a liitle carbon build-up. So I figure I'm a little on the rich side and I adjusted the clip on my main needle, no improvement. Should I be checking the ignition timing, or all my problems in the carb? When I rebuilt the carb, I used all the OEM jet and needle sizes. Any suggestions on what I should look for would be much appreciated. Thanks
Help with a KE175
- Thread starter bajus22
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dirt bike dave
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- May 3, 2000
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It's normal for a motor to rev higher in neutral than it will under heavy load.
Try a new plug first.
And it is probably jetted too rich on the main jet, especially if you are at altitude.
I'd look at those two things before playing with timing or other jets.
BTW, many of the exhausts on those old dual sports were very restrictive and not well designed for high rpm performance. There was a thriving aftermarket in exhaust pipes for those bikes back in the day, but most of the makers are long gone.
Try a new plug first.
And it is probably jetted too rich on the main jet, especially if you are at altitude.
I'd look at those two things before playing with timing or other jets.
BTW, many of the exhausts on those old dual sports were very restrictive and not well designed for high rpm performance. There was a thriving aftermarket in exhaust pipes for those bikes back in the day, but most of the makers are long gone.
- Thread starter
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- #3
So I put in the new plug, and changed the the main jet from a #102.5 to a #97. I went out for about 10 miles, and the temp was about +2 celcius, and all I could manage was 42mph. At WOT and top gear the bike just bogs down and I lose all power and speed. After the ride, I checked the plug it looked good, no carbon fouling. So should I advance or retard the timing. Is there anything else I should check?
snowskater101
Member
- Jul 18, 2007
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check your ground cable. it could possibly be loose and at high speeds there's a lot more vibration, it could be missing the ground and losing spark thus not firing.
dirt bike dave
Sponsoring Member
- May 3, 2000
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Check to see if the exhaust is clogged up. It's doubtful that it has a rebuildable silencer, but years and years of running rich could have gummed up the pipe.
Make sure the fuel tank is venting properly (under load you need to suck in more fuel, and if the tank vents are clogged it can restrict fuel flow).
If there is a fuel filter in the fuel line, remove it or replace it with a new one.
Make sure the petc*oc*k inside the fuel tank is not clogged with debris.
Is the air filter clean and not over-oiled?
Does the bike pull strong and rev out in the lower gears and just peter out in top gear, or is it weak in every gear?
How many mph will it top out at in 4th gear?
Will it pull in top gear if you slowly and steadily give it more throttle? Does it only bog if you whack the throttle wide open?
Make sure the fuel tank is venting properly (under load you need to suck in more fuel, and if the tank vents are clogged it can restrict fuel flow).
If there is a fuel filter in the fuel line, remove it or replace it with a new one.
Make sure the petc*oc*k inside the fuel tank is not clogged with debris.
Is the air filter clean and not over-oiled?
Does the bike pull strong and rev out in the lower gears and just peter out in top gear, or is it weak in every gear?
How many mph will it top out at in 4th gear?
Will it pull in top gear if you slowly and steadily give it more throttle? Does it only bog if you whack the throttle wide open?
- Thread starter
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- #6
I'm not sure how to tell if the exhaust is plugged up, but I do get alot of smoke coming out of it when I rev in neutral. The tank vent is clean, so I assume it is venting properly. I've already replaced the fuel filter, put in a new air filter (oil is good, not too much), and the petcock is good and clean. The bike bogs down in every gear past 6,000rpm. Top speed in fourth is about 42mph. In top gear it will pull (only slightly) if I'm slow and steady on throttle, but once the throttle is past 1/2 open, it bogs down, like it's not getting any fuel. Would the bowl level have an effect on this?
dirt bike dave
Sponsoring Member
- May 3, 2000
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If your float level is too low, you could be running the carb dry under sustained heavy load. Try raising the float level - it might be as simple as bending the tab that holds the float.
You might be able to find a .pdf diagram of your motor and exhaust pipe at www.buykawasaki.com This can give you a good idea of where any screens are that might get clogged in there. Since it is going to be hard to find a replacement, you might have to do some pipe surgery.
With enough room and a level straight road and no headwind, IMO your bike should have enough power to pull well over 60 mph. Whether or not the rest of the bike is safe to go that fast is another story, lol.
Good luck getting it sorted out! As mentioned earlier, it could be ignition related, but I suspect fuel starvation or blocked exhaust.
You might be able to find a .pdf diagram of your motor and exhaust pipe at www.buykawasaki.com This can give you a good idea of where any screens are that might get clogged in there. Since it is going to be hard to find a replacement, you might have to do some pipe surgery.
With enough room and a level straight road and no headwind, IMO your bike should have enough power to pull well over 60 mph. Whether or not the rest of the bike is safe to go that fast is another story, lol.
Good luck getting it sorted out! As mentioned earlier, it could be ignition related, but I suspect fuel starvation or blocked exhaust.
- Thread starter
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- #8
Well, I adjusted the float, and the bike felt alot better. I was able to get to 55mph, but I ran out of road and I got too cold (it was -14 degrees celcuis here). Funny thing was, I was almost able to go to redline in fourth gear (and I was at 55mph), and everything felt fine. But as soon as I dropped it into fifth, I lost speed, power, and I couldn't get it past 6,000rpm.
dirt bike dave
Sponsoring Member
- May 3, 2000
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Top gear might just be too tall, and you are falling out of the powerband when you shift up from fourth. The stock gearing on some of those old dual sports was often too tall. You might actually be able to pick up top speed by putting on a larger rear sprocket, or dropping a tooth on the front sprocket. This should also improve accelleration, and make the bike better on the trail, too.
Never had to clean out an old pipe, but first try to find out if you can rebuild or repack the silencer/spark arrestor portion. It is very possible that there are some sort of perforations in there that have clogged up. Many of those old pipes were very poor from a performance perspective, and even if it is not clogged up, the pipe could really be choking off the power.
Never had to clean out an old pipe, but first try to find out if you can rebuild or repack the silencer/spark arrestor portion. It is very possible that there are some sort of perforations in there that have clogged up. Many of those old pipes were very poor from a performance perspective, and even if it is not clogged up, the pipe could really be choking off the power.
High RPM trouble?
I had a similar problem with my 76 KE175. I replaced the small o-ring at the bottom of the needle jet holder (it was not sealing completely & was allowing extra fuel to get past the main jet at high revs). This solved the problem immediately. (oem part#92055-044, but I just took the needle jet & the float bowl to a local auto parts store & they found an o-ring that fit perfectly. I hope this helps.
bajus22 said:Well, I adjusted the float, and the bike felt alot better. I was able to get to 55mph, but I ran out of road and I got too cold (it was -14 degrees celcuis here). Funny thing was, I was almost able to go to redline in fourth gear (and I was at 55mph), and everything felt fine. But as soon as I dropped it into fifth, I lost speed, power, and I couldn't get it past 6,000rpm.
I had a similar problem with my 76 KE175. I replaced the small o-ring at the bottom of the needle jet holder (it was not sealing completely & was allowing extra fuel to get past the main jet at high revs). This solved the problem immediately. (oem part#92055-044, but I just took the needle jet & the float bowl to a local auto parts store & they found an o-ring that fit perfectly. I hope this helps.
- Thread starter
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- #12
Yep, I replaced that O-ring too. But I'm starting to wonder if it might be a slipping clutch. I went for another ride, and I have decent power and pull up until 6,000 rpm, and then no pull, but the engine will increase it's revs. The revs bounce between 6,000 to 7,500rpm. And when I pulled into the garage the bike smelled funny. I've never experianced a slipping/worn clutch before, but from what people have told me, I should probably check that too.
2strokerfun
Member
- May 19, 2006
- 1,500
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Sounds like you might have it (or at least part of it). In my experience, first sign of worn clutch plates is high-speed slipping. Quickly followed by complete slipping. And the amount of time it takes for clutch plates to quit grabbing completely seems to be inversely proportional to the distance from my truck.
I had nearly the same symtoms on my old ke175. I finally cut into the side of the pipe (inside) and found the spark arrester was severly clogged so I cut it out and put a 1" pipe between the stinger and the tail pipe. This made a big difference in power and noise but I only did this to race in my first vmx race. I also put a slightly larger main jet in.
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