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Discussion Starter · #1 ·
I just bought this very nice cb400. The mechanic I bought it from said the stator was bad and I should not go over 4500 rpm's until I replace it. He also said that a good stator will make the motorcycle go faster. I took it to another mechanic who told me that the stator was fine and even if it was bad it wouldn't effect the speed of the motorcycle. The second mechanic rebuilt the carbs and tuned it up and the motor runs great. The top speed I am getting out of it is 62mph. This motorcycle is all stock parts. The 2nd mechanic told me that 60 65mph is as fast as this motorcycle will do with the stock exhaust, carb jets, and intake. I think I read that this motorcycle should do top speed of 90mph with stock parts. Can anyone tell me if that is true? If so can you tell me how to test the stator and what to tell my mechanic about this issue. Thanks.
 

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I just picked up a 400a (the automatic version) bone stock and I could run 70+ all day and I'm a porkey 225. the auto isn't as quick as a 5speed. even at 70 there was more throttle to go and more engine to pull it. long story short, it should be able to much more in my opinion. I also on occasion ride my wifes 250 rebel and same story.
 

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First off, welcome to the site.

It can most definitely go faster than 60 mph. It should be able to at least go 85 to 90 mph. If your topping out at 60 or so then there must be something preventing it. Are you in the top gear? If so, it could be a number of things like low compression, clogged or partially clogged jets, dirty air filter, mis-adjusted clutch, spark plugs. Does it run good up until 60? What then happens when you get up to 60?
 

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I see you got a couple of answers while I was figuring out what to tell you.......

The stator is strictly part of the charging system although it does contain additional coils and pick-ups that signal the electronic ignition module......So, it's definately NOT anything to do with the stator itself (as far as top speed)....

Mechanic #2 is correct about the stator....BUT, if he had correctly checked out and "tuned-up" the engine, cleaned and set the carbs, the bike would run much faster than low 60's....OR, he would have at least found out WHY/THAT it won't go any faster during his "test ride"....(I suspect weak/bad rings/low compression as the valve ajustment and carbs have already been done during the "tune-up"

My 1970's 175 Honda will do over 70MPH ..... Just FYI.....
 

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superstar said:
I just bought this very nice cb400. The mechanic I bought it from said the stator was bad and I should not go over 4500 rpm's until I replace it. He also said that a good stator will make the motorcycle go faster. I took it to another mechanic who told me that the stator was fine and even if it was bad it wouldn't effect the speed of the motorcycle. The second mechanic rebuilt the carbs and tuned it up and the motor runs great. The top speed I am getting out of it is 62mph. This motorcycle is all stock parts. The 2nd mechanic told me that 60 65mph is as fast as this motorcycle will do with the stock exhaust, carb jets, and intake. I think I read that this motorcycle should do top speed of 90mph with stock parts. Can anyone tell me if that is true? If so can you tell me how to test the stator and what to tell my mechanic about this issue. Thanks.

How many rpms are you showing at 62mph?
 

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Discussion Starter · #6 ·
1971 CB450 said:
superstar said:
I just bought this very nice cb400. The mechanic I bought it from said the stator was bad and I should not go over 4500 rpm's until I replace it. He also said that a good stator will make the motorcycle go faster. I took it to another mechanic who told me that the stator was fine and even if it was bad it wouldn't effect the speed of the motorcycle. The second mechanic rebuilt the carbs and tuned it up and the motor runs great. The top speed I am getting out of it is 62mph. This motorcycle is all stock parts. The 2nd mechanic told me that 60 65mph is as fast as this motorcycle will do with the stock exhaust, carb jets, and intake. I think I read that this motorcycle should do top speed of 90mph with stock parts. Can anyone tell me if that is true? If so can you tell me how to test the stator and what to tell my mechanic about this issue. Thanks.

How many rpms are you showing at 62mph?
7500rpms and that is pegged.
 

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Discussion Starter · #7 ·
66Sprint said:
I see you got a couple of answers while I was figuring out what to tell you.......

The stator is strictly part of the charging system although it does contain additional coils and pick-ups that signal the electronic ignition module......So, it's definately NOT anything to do with the stator itself (as far as top speed)....

Mechanic #2 is correct about the stator....BUT, if he had correctly checked out and "tuned-up" the engine, cleaned and set the carbs, the bike would run much faster than low 60's....OR, he would have at least found out WHY/THAT it won't go any faster during his "test ride"....(I suspect weak/bad rings/low compression as the valve ajustment and carbs SHOULD have already been done during the "tune-up"

My 1970's 175 Honda will do over 70MPH ..... Just FYI.....

that is good to know. thanks. I will pass it on to mechanic #2 and keep you posted.
 

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How many rpms are you showing at 62mph?[/quote]

7500rpms and that is pegged.[/quote]

Throttle pegged?.....Or tach pegged?

Usually 7500RPM in top gear would be at least 75MPH (indicated)..... Mechanic#2 presumably adjusted everything correctly during tune-up as the engine runs well.
The problem could be in power transfer to the wheel.....
Could be a slipping clutch........
Final drive ratio lowered.....
"dragging" brakes (holding you back).....
"binding" drive chain..

OR, not enough power to transfer....( low compression numbers)..."running well" does not necessarily mean producing good usable power.....
"Normal" compression for the 400's is 185 PSI.....
 

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I think 7500 rpm is not redline on your tach? Is it? Count the teeth on your front and rear sprocket. I have a feeling someone has geared your back down. I could be wrong.
 

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Discussion Starter · #10 ·
HerrDeacon said:
First off, welcome to the site.

It can most definitely go faster than 60 mph. It should be able to at least go 85 to 90 mph. If your topping out at 60 or so then there must be something preventing it. Are you in the top gear? If so, it could be a number of things like low compression, clogged or partially clogged jets, dirty air filter, mis-adjusted clutch, spark plugs. Does it run good up until 60? What then happens when you get up to 60?


yes I am in top gear and have it wide open at 7500rpm. It does run great especially after I had the carbs rebuilt and the air filter and spark plugs changed. but still wont go over around 62 down hill. at around 60 mph it just doesnt give me anymore speed. it does not bog or anything weird like that.
 

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I comfortably cruise at 65 mph, and have easily hit 70 - 75, but haven't wanted to go faster, although I could.

I don't remember exactly, but I'm pretty sure I'm not at 7500 rpms at 60 mph, maybe closer to 6000 - 6500???

I'm no expert, but I know people change sprockets to get better acceleration at the expense of top speed. Doing this would be good for being quick off the line and around the city. That might be worth checking out...
 

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superstar said:
yes I am in top gear and have it wide open at 7500rpm. It does run great especially after I had the carbs rebuilt and the air filter and spark plugs changed. but still wont go over around 62 down hill. at around 60 mph it just doesnt give me anymore speed. it does not bog or anything weird like that.
If the rpm's are not going above 7500 at that point then its probably not a slipping clutch since the rpms would go higher without any increase in speed.

Like some of the other guys said here, the PO may have swapped the sprockets for more low end speed, worth counting the teeth on the front and rear sprockets so you can compare to the stock ones. Otherwise, it could be a carb issue, maybe a clogged main jet or something.
 

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Agreed...we're pretty much down to a sprocket (gearing) change has occurred....But it still could be an improperly seated spring in the carbs (although less likely)....
 

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I just got back from a quick spin to blow the dust off my jacket. My 450, maybe geared different, is at about 5500 rpm at 62mph ish. One more thought, could you speedo be wrong? Does it feel like you are going fast? I got up to almost 80 last week and my face was peeled back, no helmet law in PA.
 

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1971 CB450 said:
I just got back from a quick spin to blow the dust off my jacket. My 450, maybe geared different, is at about 5500 rpm at 62mph ish. One more thought, could you speedo be wrong? Does it feel like you are going fast? I got up to almost 80 last week and my face was peeled back, no helmet law in PA.
You may be on to something there Ben. My old KZ had issues like that with the speedo. Had it up to 95mph one time, continued to accelerate but when I looked at the speedo it was at 60mph :shock: Never worked after that, wouldn't go past 60 anymore.
 

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HerrDeacon said:
1971 CB450 said:
I just got back from a quick spin to blow the dust off my jacket. My 450, maybe geared different, is at about 5500 rpm at 62mph ish. One more thought, could you speedo be wrong? Does it feel like you are going fast? I got up to almost 80 last week and my face was peeled back, no helmet law in PA.
You may be on to something there Ben. My old KZ had issues like that with the speedo. Had it up to 95mph one time, continued to accelerate but when I looked at the speedo it was at 60mph :shock: Never worked after that, wouldn't go past 60 anymore.

I am not sure how but my speedo is kinda vague, maybe worn out or something? It will kind of bounce around slightly and seemed to go from 60 to 85 very quick, not sure if it was lagging behind or just bouncing, it works ok but I don't trust it 100%
 

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My CT90 gets over 50 mph, no way this bike is running right.

Are you sure the tach is working right? Does it advance smoothly through the rpms to the redline? My old tach was binding up, would shoot up to redline and stay there above a certain actual rpm.

If your tach is actually working and you truly are achieving 7.5k rpm, then I think it has to be one of these problems:

1. Your clutch is slipping.

2. Your bike has been regeared for more power at lower speed.

3. You have a Hondamatic transmission and you are not switching it from low to high gear.

If it is #3, I am expecting some sort of prize for me, here. :mrgreen:
 

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66Sprint said:
Usually 7500RPM in top gear would be at least 75MPH (indicated)..... Mechanic#2 presumably adjusted everything correctly during tune-up as the engine runs well.
The problem could be in power transfer to the wheel.....
Could be a slipping clutch........
Final drive ratio lowered.....
"dragging" brakes (holding you back).....
"binding" drive chain..

OR, not enough power to transfer....( low compression numbers)..."running well" does not necessarily mean producing good usable power.....
"Normal" compression for the 400's is 185 PSI.....
If the 7.5k rpm is correct, then it has to be either regearing, or slipping clutch. Dragging brakes or binding would slow down the engine, and not enough power would mean engine would bog down under load, right?
 

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superstar said:
7500rpms and that is pegged.
Okay, my bad, I thought this meant that the needle on the tach was pegged. Not so, obviously, as this is a '78 tach:



In that case, yes, it could be something holding the bike back, like binding, or something robbing power, in addition to it being re-geared, or not in top gear.
 

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Fit a sat nav to the bike to check top speed, sounds like the sprocket has been changed on the front, +1 or +2 teeth is it quick off the mark will it keep up with the power ranger brigade from the lights?
 
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