wide open throttle trouble

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Dougr
Posts: 11
Joined: Mon Jul 07, 2014 3:33 pm

wide open throttle trouble

Postby Dougr » Mon Jul 14, 2014 3:22 pm

As a first time Street bike owner iam very happy to own a 1981 CB650. My bike has 14,000 kms on it and starts and runs fine but when I go wide open throttle in 5 gear it starts to stumble at 5000 rpm and will not go past 100 kms per hour. the fuel is clean and i have tryed some carb cleaner in the fuel have installed new spark plugs replaced the plug wires and air filter also by-passed the auto fuel shut off. anybody have some advise short of removing the carbs and having them gone threw. Thank you....Doug

cb650
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Re: wide open throttle trouble

Postby cb650 » Mon Jul 14, 2014 4:39 pm

Many threads on that. Easy thing to try is with out your air filter. Then we can go from there. And a little more detail on the bike. Does it even have the stock filter?
Did you clean the tank out?!?!?!?!

Dougr
Posts: 11
Joined: Mon Jul 07, 2014 3:33 pm

Re: wide open throttle trouble

Postby Dougr » Tue Jul 15, 2014 6:08 pm

The filter is a stock one and just replaced. I have not cleaned out the tank but I have run 3 tanks full threw it now and I drained out a quart into a glass jar and saw no stuff ( rust or otherwise ) in the fuel. The Bike is all orginal no mods at all

Dougr
Posts: 11
Joined: Mon Jul 07, 2014 3:33 pm

Re: wide open throttle trouble

Postby Dougr » Sun Jul 20, 2014 9:33 am

Just got the bike back from the shop where I had the fork seals replaced. My mechanic suggested that I run the bike with out the air filter just as you did cb650. Boy what a difference that made The Honda nows revs freely to 9000 rpm in the the first 3 gears and pulls hard. in 5th gear I still notice some surging have not had it past 130 kms yet. Seems like the stock air filter is holding it back any suggestions? Also I have treated the fuel with SeaFoam, have not used up the tank full yet if it stops raining I can get some more kms on her.
Tks...Doug

cb650
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Re: wide open throttle trouble

Postby cb650 » Sun Jul 20, 2014 4:31 pm

Your main jets are a little big. Put in a K&N filter.
Did you clean the tank out?!?!?!?!

Dougr
Posts: 11
Joined: Mon Jul 07, 2014 3:33 pm

Re: wide open throttle trouble

Postby Dougr » Mon Jul 21, 2014 8:57 am

Got a K&N filter on order thank you for your help cb650

Dougr
Posts: 11
Joined: Mon Jul 07, 2014 3:33 pm

Re: wide open throttle trouble

Postby Dougr » Thu Aug 28, 2014 4:59 pm

Tryed the KN filter made no Difference... but I got it fixed now removed the carbs and had my bike mechanic go threw them while they were dirty we found the jets were all correct the problem turned out to be the Carb bowl vent hoses were split open ( dry rotted) and venting to atmosphere no longer hooked up to the air box once that was repaired the Honda will now rev up to red line with a air filter installed.

FordMan
Posts: 130
Joined: Fri Jul 18, 2014 10:20 pm
Location: Southern Minnesota

Re: wide open throttle trouble

Postby FordMan » Fri Aug 29, 2014 12:35 am

cb650 wrote:Your main jets are a little big. Put in a K&N filter.


Why would fat jets need a K&N Filter?

Mine runs fat, and has a NOS OEM filter, and it pulls hard to redline.
I understand the better airflow, but.... idk

Grats on getting it fixed OP, now make sure u store it correctly in the winter (if u have winter see u posted Km's per hour) so u dont have to go thru it in the spring. ( i always store with non-ox fuel as well)
"Vintage Revolution"
https://www.youtube.com/channel/UCOrn_h ... DZhOPmH81w
Current:
1979 Honda CB650 (HardTail Build)
1983 Suzuki GS850L (Fix and Minor Restore)
Old:
1989 Suzuki Katana 600
1978 Honda CB400T "Hawk"
1983 Honda VF750

cb650
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Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
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Re: wide open throttle trouble

Postby cb650 » Fri Aug 29, 2014 7:48 am

Big jets need more air. a k&n will supply a little more air.
As we find out all bikes are diff. what works for one might not on another.
Did you clean the tank out?!?!?!?!

FordMan
Posts: 130
Joined: Fri Jul 18, 2014 10:20 pm
Location: Southern Minnesota

Re: wide open throttle trouble

Postby FordMan » Fri Aug 29, 2014 4:22 pm

I have installed K&N filters on a wide range of things i have owned, and i have never ever had any kind of "significant" benefit, besides no longer throwing away a bunch of used filters.

I like them for the reusable factor more than actual performance, i am sure with a dyno or wide band o2 we can see a difference, but have never went "oh man thats 30hp i can feel that filter doing its job"ya know.
"Vintage Revolution"
https://www.youtube.com/channel/UCOrn_h ... DZhOPmH81w
Current:
1979 Honda CB650 (HardTail Build)
1983 Suzuki GS850L (Fix and Minor Restore)
Old:
1989 Suzuki Katana 600
1978 Honda CB400T "Hawk"
1983 Honda VF750

cb650
Posts: 2959
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
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Re: wide open throttle trouble

Postby cb650 » Sat Aug 30, 2014 11:24 am

yea hard to get 30 hp out of a engine that only does 54 or so with just a filter change. I never said it was gods answer to the problems of the world.
In the margins it helps. said it supplied a LITTLE more air. Turns out wasnt his problem but now he does have the benefit of the also reusable K&N. Any reason you need to keep pushing this?
Did you clean the tank out?!?!?!?!

FordMan
Posts: 130
Joined: Fri Jul 18, 2014 10:20 pm
Location: Southern Minnesota

Re: wide open throttle trouble

Postby FordMan » Sat Aug 30, 2014 11:51 am

I'm not trying to push the issue, i was just trying to find your reasoning for the K&N is all. It seems like it was a blind shot in the dark, as a recommendation.
I was just stating that i havent seen K&N's make a big enough difference to significantly change the Air to Fuel ratio.

IMO K&N's should go on perfectly running engine's that need a small boost in moving Air, not trying to solve a possible air to fuel ratio problem, but again thats MY opinion.

I am not trying to pick a fight or start a personal attack, i just was simply trying to understand your reasoning is all.
"Vintage Revolution"
https://www.youtube.com/channel/UCOrn_h ... DZhOPmH81w
Current:
1979 Honda CB650 (HardTail Build)
1983 Suzuki GS850L (Fix and Minor Restore)
Old:
1989 Suzuki Katana 600
1978 Honda CB400T "Hawk"
1983 Honda VF750

cb650
Posts: 2959
Joined: Fri Mar 03, 2006 7:20 am
Location: Denver CO USA
Contact:

Re: wide open throttle trouble

Postby cb650 » Sun Aug 31, 2014 7:18 am

OP said it ran better without a filter. K&N might have worked especially with a jet change. Yes it was a shot. I cant see the bike o everything is a shot in the dark. As it turns out nobody was right. Do you by chance own a 5.0 mustang?
Did you clean the tank out?!?!?!?!


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