1981 CB750 Super Sport

[shinyribs]

Maybe if you listen real close you can hear it squirt?

I dunno,but I DO know you've jinxed me My bike started doing this today. Sitting at a light and the idle just slowed down a little then died. Cranked right back up and then died again.I went through a couple traffic signals like this-having to use the throttle to maintain idle. But my power was completely unaffected. I just reached under the tank and cranked the idle speed up a bit and it was fine from there on. Later in the evening after it had cooled off it was idling too fast so I backed it back down to ''normal''. Weird. Never done this before. Almost seemed like some sort of vapor lock situation. I popped the cap of the fuel tank to check for a ''woosh'' but nothing,so it's not related to tank venting apparently.

But this particular instance happened to be at the point where my bike was the hottest it's ever been. I was tearing up some back roads pretty good but road work detoured me straight into city traffic. I didn't have my usual 2-3 miles of ''cool down'' period I usually give the bike before I jump back in to normal traffic.I've been noticing that ever since I put the stock airbox back on the bike has been running warmer. I dont have an oil temp gauge anymore,but I think I may put it back on there. I never remember the engine feeling this warm to the touch before. I cant even lay my hand on the stator or points cover.

Sorry for the long post,just trying to throw as much info as possible out there and see if something might relate to your issue. Even though I'm on a lowly SOHC,it sounds like the same thing.

[Johnnylevi]

It does sound similar. Does yours for when you put load on it and make you look like a newbie rider too? Mine does the same thing as far as when it warms up it starts to die. I'm goin to mess with my fuel mixture to see if that helps at all. Doesn't it say something of your bike performs worse when warm?

[Hoosier Daddy]

Just to muddy the waters a little bit...
A marginal coil will start to breakdown when it's hot.
Maybe totally unrelated, and doesn't explain why it would restart right away.

[shinyribs]

My thoughts exactly Hoosier Papa. But the easy restart, like you said, makes me want to not think its the coil.  I wish I would've reached under and a fuel bowl to check for temperature.  See if it had gotten hot enough to vapor lock or boil off. Strange.

[Johnnylevi]

I think I've figured out my problem. When I started it last night and for that matter the other day it would idle with no choke... I figured since it was 90 the other day that it was already pretty warm, but last night it was about 55. So I'm pretty sure my mixture is just rich. Going to mess with the screws when I get the handy tool back from my friend. See how that goes and then change my coils to the F3 and spark plugs to iridium and see how everything does together

[seestheday]

I would recommend making one change at a time.  It's best to only be
working with one variable.

[Johnnylevi]

sorry thats What I meant by all that. It wasn't very clear. I meant adjusting the fuel air mixture and then after that works (if it does) putting the new coils and plugs on.

[shinyribs]

Sounds like a good plan to me. It occurred to me that it's been about... 14-15k miles since I set my bike up. I think I might just check the sync on my carbs.Shoot,they may need a little bit of a cleaning at this point.

My bike did it again today. The bike wasn't as warm as before,and the problem wasn't as severe. I just noticed a little drop off of rpm's at idle. Definitely heat related(for me at least)just gotta find the cure.

[Johnnylevi]

Sounds like a good idea to sync em up again. Can't desyncronized carbs make the bike run warmer?

[Hoosier Daddy]

if it causes a lean condition... say for example one or two throttle plates don't open as far as they should could cause a lean condition on those cylinders. But I think it would have to major differance at anything above idle.
Lean engines run hot, rich engines run cooler but can load up at lower RPM.

[Johnnylevi]

Put some work in on the bike today. Put in the Cbr coils. OH MAN! What a difference!!!! my bike starts cold with just a push of the button. If any of you DOHC guys dont have this upgrade do it! my bike revved to 7k with so much ease. oh and i painted the rest of the bike

[shinyribs]

 Very nice. Very,very nice!

[Johnnylevi]

Just ordered some new ignitors  http://www.ebay.com/itm/111068386673?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Supposedly this in combination with my CBR F3 coils will really make my bike start/charge/rev better! Got the stock jets too. Any way to install em without taking the carbs off?

[seestheday]

Definitely need to pull the carbs to change the jets.

Sent from my BlackBerry device

From: Johnnylevi [via Honda CB750'S]

Sent: Friday, June 14, 2013 9:06 PM

To: seestheday

Subject: Re: 1981 CB750 Super Sport

Just ordered some new ignitors  http://www.ebay.com/itm/111068386673?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

Supposedly this in combination with my CBR F3 coils will really make my bike start/charge/rev better! Got the stock jets too. Any way to install em without taking the carbs off?

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[Johnnylevi]

Holy 105's batman! Wow. Before I put these guys in my bike didn't really want to go above 7k It would bog even at 6k and then come back up. With these 105's it goes to 9k no problem. Sounds a lot healthier too. Just gotta get my ignition timing cover leak and Cam chain B tensioner leak sorted out.

[seestheday]

Are you able to find a cam chain tensioner from the dealership?

I heard a rumour they were now nla...

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From: Johnnylevi [via Honda CB750'S]

Sent: Saturday, June 15, 2013 5:56 PM

To: seestheday

Subject: Re: 1981 CB750 Super Sport

Holy 105's batman! Wow. Before I put these guys in my bike didn't really want to go above 7k It would bog even at 6k and then come back up. With these 105's it goes to 9k no problem. Sounds a lot healthier too. Just gotta get my ignition timing cover leak and Cam chain B tensioner leak sorted out.

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[Johnnylevi]

I have not been able to find one. I'll let you know if I do. I think our best option is captains tensioner. It's a tight squeez in a 750

[seestheday]

I thought captains was for the a chain?

Sent from my BlackBerry device

From: Johnnylevi [via Honda CB750'S]

Sent: Saturday, June 15, 2013 9:18 PM

To: seestheday

Subject: Re: 1981 CB750 Super Sport

I have not been able to find one. I'll let you know if I do. I think our best option is captains tensioner. It's a tight squeez in a 750

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[Johnnylevi]

You are probably right. I got the letter mixed up awhile back so I automatically think its opposite of what I remember it as.

[Johnnylevi]

Hey guys, Got a new points cover yesterday, so just waiting on the O-ring for my Cam chain tensioner and then My bike will be leak free! Starts like a champ. I also put the 438 ignition timing module thingy. It actually fixed my stuttering in the 2-3k range... or at least thats the only thing thats changed since I last started my bike. Going to get ahold of a go-pro and get some video for you guys soon .

Didnt think I wouldve gotten this bike going without you guys so thanks so much!