Honda Aero 80 drop in top speed

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hondafan
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Honda Aero 80 drop in top speed

Post by hondafan »

In the last week my Aero went from the normal 43 mph to about 35-36. I did the belt and rollers about 200 miles ago. Also cleaned the carb during the winter and recently decarbed the muffler. I took the muffler off yesterday and it is clean and the exhaust port is clean. When I go wot the speed goes even lower, if I back off it seems to run better but won't run like it is supposed to. Anyone know what could be going on here?
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Re: Honda Aero 80 drop in top speed

Post by patthesoundguy »

hondafan wrote:In the last week my Aero went from the normal 43 mph to about 35-36. I did the belt and rollers about 200 miles ago. Also cleaned the carb during the winter and recently decarbed the muffler. I took the muffler off yesterday and it is clean and the exhaust port is clean. When I go wot the speed goes even lower, if I back off it seems to run better but won't run like it is supposed to. Anyone know what could be going on here?
That doesn't sound like a happy scooter. Is there an issue with the vacuum auto bysatarter, maybe its stuck in the enrich mode. There is a way to make it manual, its here on the board not sure where though. Check for a clogged screen in the tank maybe its not getting too fuel flow.


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Re: Honda Aero 80 drop in top speed

Post by hondafan »

I checked the fuel screen and fuel filter. It is flowing as it should. I thought about the bystarter but didn't want to mess with it because acceleration and all else is fine. Do you thing my variator may or clutch maybe bad. I was stuck on this exact speed two months ago and I noticed a gradual decline util this week where I lost about 5 mph.
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Re: Honda Aero 80 drop in top speed

Post by dun rite »

probably a good idea to check rollers again before tearing things apart in the motor
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Re: Honda Aero 80 drop in top speed

Post by patthesoundguy »

[quote="dun rite"]probably a good idea to check rollers again before tearing things apart in the motor[/quote
Yes fun rite is on to something here, you can pull the cover and check the operation of the variator with the scooter on the stand, maybe the belt is not riding up as high as it was, maybe the belt is wearing out quickly for some reason. Measure the belt width and check it to the manual spec.

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Re: Honda Aero 80 drop in top speed

Post by breaze »

+1 on opening up that left side cover and checking things out - if belt and rollers are only 200 mile old, probably ok but worth checking out.

What year is your Aero 80? Mine is an 85 and has the thermal/vacuum choke - if yours has that type choke, here is a quick link to how to by-pass it - either temporarily to make sure it is working correctly or permanent:

http://www.hondaspree.net/phpBB3/viewto ... ze#p234931

If you use clear lines on that choke, it is pretty easy to tell if it is working properly (nothing should be flowing once warmed up).


Also, did you change to a 90 main jet? As I recall, these 80's have a tendency to bog out at wot and that is the suggested fix.

good luck
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Re: Honda Aero 80 drop in top speed

Post by hondafan »

It is a 1984. Prior to changing the rollers and belt I was hitting a top speed of 36. After changing everything I was back up to about 43 mph. Then I gradually started losing top end speed and now I am back at 36. When I am at that speed it is with my throttle a little past half way opened. If I twist it more it sounds like a horrible bog and I lose more top end. Acceleration is fine to 36 and it pulls strong to that point. It started dropping after I added a little seafoam to the tank. I am thinking this may have screwed something up with the bystarter which has multiple hoses.
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Re: Honda Aero 80 drop in top speed

Post by breaze »

Looks like the 84 does have the thermal operated choke - to see if your choke is causing your problems, you can simply cap off the nipples on the intake and carb once the engine is warmed up (taking the choke completely out of the equation) and see if it resolves anything. Check that link for a description of how it works and how to troubleshoot Clear hoses are inexpensive and your hoses should probably be switched out anyway if you haven't already - especially if you still have the original 25 year old hoses on there.

Also, the up-jet to a 90 main jet is a tried and true recommendation for all Aero 80's. It is specifically for the bogging at wot problem. While it is odd that you would be running fine and slowly develop this problem, up-jetting is cheap and easy and will benefit you even if it does not resolve your specific problem.
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Re: Honda Aero 80 drop in top speed

Post by Wheelman-111 »

Greetings:

If closing the throttle a little (less air) improves power, and if it ran well previously, the first thing I'd do is check for a vacuum leak.
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Re: Honda Aero 80 drop in top speed

Post by patthesoundguy »

The donut gromet that attaches the air box to the carb is a weak point and if the rear fender assembly is loose the donut wears and can pull off the carb. The air filter should be something else to look at, if its unknown on its age replace asap. The new carb donuts gasket is much improved over the original factory one. I have one for my aero and replaced the one on my friends aero last year,her aero had the issue of the fender / air box floating around not attached to any thing causeing issues. And put a 90 jet in it no matter what. It makes a massive difference in drivability, Thanks Bear B-) I've done it on my aero and also on my friends aero. I put dual stage reeds on both as well B-)

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Re: Honda Aero 80 drop in top speed

Post by hondafan »

Thanks all for the advice I will check on all these things and let you know what works.
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Re: Honda Aero 80 drop in top speed

Post by hondafan »

Would a bad bystarter give off the symptoms I am having. I have absolutely no sputtering and the motor pulls strong up to 36 mph at that point I can't keep the throttle wide open I have to bake off quite a bit. I feel like it wants to go faster but something is holding it back, it won't move off that speed. Even down hill it will have trouble going a couple of mph more.
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Re: Honda Aero 80 drop in top speed

Post by patthesoundguy »

I found out while experamenting with my spree jetting that when it was too rich it would behave like that. You would be wide open and it would kinda bog almost then you would back off a bit it would go much faster.

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Re: Honda Aero 80 drop in top speed

Post by hondafan »

I can keep it wot all the way to 36 without an issue. It is at that speed where the problems start occurring.
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Re: Honda Aero 80 drop in top speed

Post by hondafan »

Well I did the manual valve bypass today only that Bear sketched only to find out that it runs the same with the manual bypass. Don't know what is causing this drop in speed. Could it be the main jet is clogged? The scooter runs flawlessly up to 36 mph but it will bog down if I twist the throttle for more power. I am only a little past half throttle and after that it is no good. Would a clogged main jet behave this way. I really think I am running rich as my plug is on the dark side. What could be going on here?
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