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Still have power problems

  • Thread starter Thread starter terrylee
  • Start date Start date
T

terrylee

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Still can't get the wife's 81 450 to go faster than 55-60 mph. She has been riding it for a while. Past work-Carbs. rebuilt with new o-rings,new carb. boot o-rings, new air filter, new plugs, new sparkplug caps, new coils,coil relay mod., new r/r, all new elec. connectors, valves adjusted, new spade fusebox, new wheel bearings, new chain, new tires, new exhust head gaskets, brakes all rebuilt,new petcock. Just checked compression and got 150 on both cylinders. Took carbs back off and cleaned all jets, openings, and checked float heights.(did change one a bit-both at about 22.7mm). Carbs screws were at 2 1/2, but after working on it today moved them down to 1 3/4-seemed to idle better there. Didn't resync. today, but had done not long ago. Plugs were a bit black with small amount of soot. Took exhust off and made sure nothing blocked, or loose inside(found nothing). Bike now seems to take off quicker, but still can't get it up to past 55 or 60 even in 5th gear, and worse if in 6th. Any ideas greatly appreciated! terrylee:(
 
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terrylee said:
Still can't get the wife's 81 450 to go faster than 55-60 mph. She has been riding it for a while. Past work-Carbs. rebuilt with new o-rings,new carb. boot o-rings, new air filter, new plugs, new sparkplug caps, new coils,coil relay mod., new r/r, all new elec. connectors, valves adjusted, new spade fusebox, new wheel bearings, new chain, new tires, new exhust head gaskets, brakes all rebuilt. Just checked compression and got 150 on both cylinders. Took carbs back off and cleaned all jets, openings, and checked float heights.(did change one a bit-both at about 22.7mm). Carbs screws were at 2 1/2, but after working on it today moved them down to 1 3/4-seemed to idle better there. Didn't resync. today, but had done not long ago. Plugs were a bit black with small amount of soot. Took exhust off and made sure nothing blocked, or loose inside(found nothing). Bike now seems to take off quicker, but still can't get it up to past 55 or 60 even in 5th gear, and worse if in 6th. Any ideas greatly appreciated! terrylee:(
Click to expand...
Does it rev up ok as you go thru gears and then just fall flat as you hit 55mph ? Did you check to make sure petcock is delivering copious amounts of fuel to carbs? Is tank vent not blocked?
 
Does rev fine through all gears till you try to get up to 50-60 in 5th gear and just seems to want to go faster, but won't. Sorry, forgot to mention, petcock is also new. I will try the gas cap, haven't cleaned that yet. terrylee
 
This might sound ridiculous, but is it possible that some how the PO rigged up a limiter or something? I find it a little weird that it will run through rev range fine and just cut in that speed range. I'd snoop around for some extra wires coming off the speedo and front wheel. I realize it sounds kind of stupid, but what have you got to lose at this point.
 
terrylee said:
Hey I'll check anything at this point. thanks terrylee
Click to expand...
Open up the ignition cover on the right side and check to see if the mechanical advance is working for the ignition should be able to grab it with your fingers and turn it, it should spring back. if it is stuck free it up.Just happened on my 1000
 
terrylee said:
Hey I'll check anything at this point. thanks terrylee
Click to expand...
A rev limiter would work in all gears, and you said it reved ok till you got to fifth and 55 mph- it's starved for fuel/air mixture. Will it go downhill at 70 mph in 5th or 6 th?
 
It will get up to 60-65 sometimes on flat area or down a hill, but still takes all it can do to get it to do that. I will check advance mec. terrylee
 
Ok, went out and tried to get mech. advance to move and spring back (it is part with small bolt through center of signal generator?) Took off sig. gen. and removed advance (has two small springs on it with small parts attached to springs),tried to get any part of it to move and wouldn't budge. Sprayed PB blaster around springs and attached part (which did seemed to have rust on them). Is there a trick to freeing this part up? terrylee:confused:
 
terrylee said:
Ok, went out and tried to get mech. advance to move and spring back (it is part with small bolt through center of signal generator?) Took off sig. gen. and removed advance (has two small springs on it with small parts attached to springs),tried to get any part of it to move and wouldn't budge. Sprayed PB blaster around springs and attached part (which did seemed to have rust on them). Is there a trick to freeing this part up? terrylee:confused:
Click to expand...
Holding the backing plate in one hand and twisting the projection (the tab that swings by signal coils), it should move slightly clockwise as springs stretch. If this is frozen, I don't see how motor reved passed 3000 rpm without lots of complaints.
 
Will recheck again tonight, couldn't seem to get it to move, but bike will rev, to 5-6000 when riding. terrylee
 
One thing I don't see mentioned are the clutch springs. Could your clutch be slipping? Bike will rev in high gear but bike won't accelerate real well. They are cheap and if original probably should be replaced. You can remove them and measure them, there is a spec in the service manual.
 
Okay, just to clarify, the bike will only rev to 6,000 in every gear?

Or just 5th?

You should be able to go faster than 60 in 3rd or 4th
 
One other thing I was thinking was gearing... are the stock sprockets on there? According to the parts fiche 16T front, 43T rear...

And just to be sure we're all on the same page with the timing advance mechanism, this is it:

IMG_1689.jpg


And yes it should move rather easily with a little pressure...
 
Sorry has new clucth springs and cleaned and measured (all in spec) plates. To be honest I don't think I have tried to get it up to 60 in 3rd or 4th gear, maybe I was afraid it would hurst something. Don't think I have had it past 6000, since I'm only trying for speed. You can get it to 55-60 and on rare times up to 65 in 5th gear, but seems to lose power when you shift to 6th gear. Also will lose speed going up a hill, and it rare it will hold speed if you give it more throttle. I feels like it wants to go faster but just not enough power to do it. terrylee
 
To get a better idea, take it out in 2nd or 3rd and try to run it up to redline and do a plug chop

It is made to rev up to redline and beyond, you know

Sounds like you have a lean condition
 
terrylee said:
Sorry has new clucth springs and cleaned and measured (all in spec) plates. To be honest I don't think I have tried to get it up to 60 in 3rd or 4th gear, maybe I was afraid it would hurst something. Don't think I have had it past 6000, since I'm only trying for speed. You can get it to 55-60 and on rare times up to 65 in 5th gear, but seems to lose power when you shift to 6th gear. Also will lose speed going up a hill, and it rare it will hold speed if you give it more throttle. I feels like it wants to go faster but just not enough power to do it. terrylee
Click to expand...
have you freed up the advance mechanism, If it is stuck it won't wind up.in one of your other posts you said you couldn't get it to move ?
 
Yeah, were are on the same page that is what I was trying to move. I swear I couldn't get it to budge. Did take bike out tonight and tried getting it to go 55-60 in 3rd and 4th gear. Could get it to go about 55 in 3rd with 7000rpms and 60-65 in 4th with about 65000 rpms. Bike seemed to have a little more get up and go in lower gears. But even though I could get it to nearly 70 in 5th it seemed to struggle to get there. Never did put it in 6th gear. It still seems to be holding back in higher gears, wants to go faster but just seems it can't.Still lost speed and power going up a hill, was only able to keep it at 55 in 5th gear. I'm hoping the small improvement might be the mec. advance working alittle better. Don't have time or energy to check it again tonight, but will do tomorrow. Also rear sprocket is stock, I will check frt. one tomorrow. Will try the plug chop suggested as soon as I can. Thanks to everyone for all the ideas,I am at my wits end. terrylee
 
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Here's another thought I had... is there something restricting the air intake? Too much oil on the filter or wrong filter or something like that? Or is there something restricting one or both of the mufflers? Grasping at straws here but just thinking of anything that could contribute...
 
pete said:
Here's another thought I had... is there something restricting the air intake? Too much oil on the filter or wrong filter or something like that? Or is there something restricting one or both of the mufflers? Grasping at straws here but just thinking of anything that could contribute...
Click to expand...
Yeah, something is not letting enough fuel/air mixture in under load; probably time to check cam/crank timing to rule out errors here.
 
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