Author Topic: Help... Float levels CB750 K2 (Read 2106 times)

BestBoy · « **on:** September 11, 2019, 08:48:53 AM »

Hi, my bike is running and idling fine but after about 4/5k its just lame. It revs all the way out but with a restricted feeling... like a fast stutter.

Ive checked the levels in the bowls (as well a loads of other stuff... plugs swap, carb clean, pod removal to stock and more).

Ive never check floats till now. What say ye? They are about 7mm below the gasket line usung the clear tube method. Would this affect the bike in the way I describe? Measurement was done on bike with bike level. Cant figure out how to post feckin pics on this forum!

MauiK3 · « **Reply #1 on:** September 11, 2019, 09:33:55 AM »

7mm below is too much, you'll need to raise it.

BestBoy · « **Reply #2 on:** September 11, 2019, 09:42:16 AM »

Thanks!

BestBoy · « **Reply #3 on:** September 11, 2019, 09:59:15 AM »

How do I post pics on this forum?

Gene · « **Reply #4 on:** September 11, 2019, 10:07:09 AM »

The best way for me is to just add them as an attachment.

PeWe · « **Reply #5 on:** September 11, 2019, 11:24:28 AM »

Jets?
My stock K2 has stock airbox.
Air screws 1 turn out ( can be +/- 1/8
Needles 4th notch from top. (Tested 3 notch, not good throttle response around 4k)
Main jets 115 ( tested 110, 120)

Your needles might be too lean if you have middle notch (3rd). It make a big difference.

If you run pods, more fuel. Main jets and maybe needles too.

Kevin D · « **Reply #6 on:** September 11, 2019, 12:16:52 PM »

Quote from: BestBoy on September 11, 2019, 09:59:15 AM

How do I post pics on this forum?

Quote from: Gene on September 11, 2019, 10:07:09 AM

The best way for me is to just add them as an attachment.

BestBoy · « **Reply #7 on:** September 11, 2019, 03:40:46 PM »

Here are the pics... Thanks!

BestBoy · « **Reply #8 on:** September 11, 2019, 03:45:43 PM »

Sorry... Ill try again...

PeWe · « **Reply #9 on:** September 11, 2019, 10:22:53 PM »

That a little bit too low level should not cause any issues as you have noticed.
Maybe if running full speed WOT for a while.

BestBoy · « **Reply #10 on:** September 12, 2019, 01:33:25 AM »

Thanks, so I guess the major issue is elsewhere! I'll not start messing about with floats.

Deltarider · « **Reply #11 on:** September 12, 2019, 01:54:58 AM »

Adjusting the floats is NOT a regular maintenance thing. Before even thinking of touching the floats look for other causes. Here are some:
Original fuellines have been changed and do not match the OEM dimensions hindering a correct fuel flow.
Petcock filter is (partly) obstructed.
Added aftermarket inline fuelfilters hinder a continuously good fuel flow.
In case your model has tiny filters over the valve inlets, check for obstruction.
Carb vent tubes are blocked, resulting in carbs not filling completely.
Insufficient tank ventilation.

BestBoy · « **Reply #12 on:** September 12, 2019, 02:19:27 AM »

Quote from: Deltarider on September 12, 2019, 01:54:58 AM

Adjusting the floats is NOT a regular maintenance thing. Before even thinking of touching the floats look for other causes. Here are some:
Original fuellines have been changed and do not match the OEM dimensions hindering a correct fuel flow.
Petcock filter is (partly) obstructed.
Added aftermarket inline fuelfilters hinder a continuously good fuel flow.
In case your model has tiny filters over the valve inlets, check for obstruction.
Carb vent tubes are blocked, resulting in carbs not filling completely.
Insufficient tank ventilation.

Ive just changed the fuel lines. I'm using 5.5mm I think. Same issue.
I dont have aftermarket filters in the line.
The fuel genuinley seems to flow in there fast, no issues. With the clear tube test the fuel came in as soon as petcock valve opened.
Aint checked the carb vent tubes!
The tank cap could do with being replaced but as I say, it flows well.

Aint syncd carbs yet - Could that fix this?
Aint check the needle position yet.

PeWe · « **Reply #13 on:** September 12, 2019, 02:38:09 AM »

"fast stutter" sounds too rich for me. If it is, the plugs must be black.
You need to know if the carbs have setup for stock filter or pods.
Impossible to answer without the status of the carb jets, filter and type of exhaust.

EDIT:
Your problem is not the floats only as you have written in your subject.
It runs bad from 4000rpm with a stuttering sound.
Airfilter is.....
Carbs are jetted....
Main jets and needles most important to know.

BestBoy · « **Reply #14 on:** September 12, 2019, 03:16:05 AM »

Thanks...

Air filter was pods but Ive converted to original. New airfilter.

When I cleaned carbs I checked jets. They were both standard. I was convinced the swop to original box would fix it hense me buying one on eBay. It didn't.

BestBoy · « **Reply #15 on:** September 12, 2019, 04:10:52 AM »

Who wants to do a diagnosis on these plugs? I replaced all these. Aint done a chop. Just a replacement. These are the ones I took out. No idea how long theyve been in. I bought the bike with the problem.

Keith · « **Reply #16 on:** September 12, 2019, 04:45:02 AM »

I just finished the carbs on my K2. I found the needles were on the lowest setting, and moved them to the middle setting. Also, vents between carb 2 and 3 were looped together, preventing the carbs from venting. New genuine float valve assemblies with floats set to 25mm. Huge improvement, but first check all basics, dwell and timing and both 1-4 and2-3 are getting full advance. Valve adjustment also.

Kevin D · « **Reply #17 on:** September 12, 2019, 04:51:27 AM »

Quote

....like a fast stutter

Have you checked the spark plug caps with an ohmmeter?
They should be 5000 ohms each (or 7500, or 10000 each)

...and you have sooty resistor plugs. What kind of riding do you do?

BestBoy · « **Reply #18 on:** September 12, 2019, 02:46:04 PM »

Thanks. I could check the needle settings.

I just bought the bike and its been doing this stutter after 4k since I got it. So, tbh, Ive only done about 20 miles of 'normal' riding. Testing primarily. Ive tested the plug and all ohm readings are ok as are those of the coils. Wonder why one of the plugs is whitish (lean?). Also, what causes the pops and bangs in the exhaust. If I roll on throttle in say 3rd gear and rev to about 6 or 7k then roll off allowing the gearbox to slow me down, dropping the revs, it pops and bangs. Sounds AWESOME but Im guessing its not right!

Gene · « **Reply #19 on:** September 12, 2019, 03:34:37 PM »

I am not an expert - keep that in mind.

Sounds to me like you're flooding when you are opening that throttle to get moving. The pops and bangs are typically unburnt fuel making it to the pipes and exploding therein. Also leading toward the idea of flooding. not enough to kill the bike but enough to slow it down.

This is my hypothesis.

Also - are you making sure to adjust the choke to open when you're riding? I know, silly question, but just making sure.

White plug = lean, yes.

BestBoy · « **Reply #20 on:** September 12, 2019, 03:38:51 PM »

Well... heres the thing about the choke...

When its closed, bike idles great. Ive found a nice place for idle screw and it sits just over 1k revs.

If I open the choke, the rpm gradually lowers and then dies sub 1k revs. Basically, the opposite to what Id expect to happen.

Gene · « **Reply #21 on:** September 12, 2019, 04:25:33 PM »

I would suggest getting the bike warmed up prior to setting the idle screw and set it with the choke open since that's the natural setting for riding. I only use the choke to start my bike and immediately open it, but I live in a warm-weather area. You may want to keep it partially closed to warm up, but set the idle once the bike is warm.

BestBoy · « **Reply #22 on:** September 12, 2019, 05:52:17 PM »

OK sorry, I think Ive explained this wrong...

By 'open' i mean closed (as in with the lever sticking out and the wee shutter thing inside closed presumably restricting air)

When its in its 'normal' position it's fine! Even when engine is cold. Idles great. When I lift it and put it the position thats suppose to make idle higher, it kills engine.

BestBoy · « **Reply #23 on:** September 12, 2019, 05:59:15 PM »

So to simplify:

When choke is open, bike is fine - even when cold.
When choke is closed, bike idle dies.

Presuming open is when the lever is flush with the bike and closed is when the lever sticks out 90deg. As in, the opposite to what Ive always thought a choke was suppose to do. Ive always thought, cold start... pull the choke (close it). In this bike its the opposite. Choke kills the engine.

Gene · « **Reply #24 on:** September 12, 2019, 06:03:34 PM »

right. ok. That seems normal to me. Especially in warmer weather. So you're not running around with the choke on.

well, could be - judging from the fuel level you showed - rather than flooding out you're just running out of fuel as previously discussed.

I'm terrible at this, sorry. If I was standing there I could be a lot more help.

News:

Author Topic: Help... Float levels CB750 K2 (Read 2106 times)