Topic: CB350F Carb / Timing Issues??

[brenden.carp]

Alright everyone...

After a lot of time researching posts on here and reading till my eyes are cross, I've decided it was time for me to post and get some up to date answers on some carb/timing issues I am having on my 72 cb350 four. I don't have a clue what the history on this bike is but since I've owned it I've only rebuilt the carbs, put on new points and condensers, new battery and tires...

Ive cleaned and rebuilt the carbs and bench synced them.. The mixture screws (on the side of the carbs) have been set 7/8 of a turn out. I got the carbs back on and started to check timing but seem to be having a difficult time with it. With the throttle cables off and the choke and idle screw set, the bike will idle at 1,200 rpm and while adjusting the timing it will take off to the races and run up in rpm uncontrollably. What is it that I may be missing or is there any ideas someone has on why this is happening!? Because of this issue, I'm not able to get the timing set with the "F" mark where its supposed to be... HELP?? 

Thanks.

[whizzer]

Check for air leaking around carb rubber boots to engine. Like loosening clamps and reseating them vigorously. Or testing for leaks by spraying something combustible around boots to see if idle increases. I use propane torch (unlit) and barely open. 

[strynboen]

is your return spring..realy pull the trottel komplet back to the adjustable stop?
 is there vear in the shaft the gas" port""s turn over?(oval holes in the kaburettor bodyes)
..a bit slock kan make idel adj almost imposibel..i have put some gas/fuel line on the shaft..abd pressed it against the trottel body..to teight a bit on a set veared aut kaburettors. and put a stronger return spring on...but that is a bad vay to fix it..one seson fix..the gas/tube handel get to hard to turn..

[brenden.carp]

I've pulled the carb boots off and cleaned them and looked for any visible signs of wear or cracks and saw nothing... Now that the carbs and boots are back on the bike, I'll try shooting something around the boots to see if there is something I missed.

[enwri]

Weak or stretched ignition advance springs? I've a 750 that when it gets to 1500 the advance starts and it will buzz up to 3000 and full advance without any more throttle.

[brenden.carp]

Im at a loss... getting pretty fed up with this bike.

Ive checked the carb boots for leaks, and nothing. They are solid as can be.

I got the timing set exactly to what everyone is saying it should be on this forum. point gaps are all set correct as well.

still with no throttle cables attached, ill get "half way through" the carb sync and the bike wants to either take off in RPM or not idle at 1200 and tries to die... there seems to be no happy medium with the tuning of these carbs! Ive been laboring over them for a couple hours after I fixed the timing issues...

WHAT AM I MISSING??

Thanks...

[flybox1]

+100 ^^^
what rebuild kits did you use?
did you replace the float valves w aftermarket ones?
TEC or ND points are the way to go.
have you done a clear tube test to verify you have the correct fuel level in the bowls

[harisuluv]

Brendan, one picture of your bike and we know your setup.  Without that, we have no idea what is happening, there have even been times where people have said they had x setup but actually didn't. 

So either tell us your detailed air and exhuast setup with all modifications, or even better do that plus pictures.

What you are describing could be multiple different issues, but I would first suspect a lean condition.  Without seeing your setup though, I'd just be guessing.

[flybox1]

your post count might prohibit direct uploading of photos...so use photobucket, and just paste the photo URL.

[brenden.carp]

Thanks for all the quick responses. This forum really is one of the best!

So for carb rebuild I bought the 4into1.com "Ultimate Carburetor Rebuilt Kit". Specs from the site are as follows:
  -Includes 4 floats with pins, and 4 carburetor rebuild kits. Made in Taiwan.
  -Each Carburetor Kit Includes:
+1.8 Needle Valve & Seat
+D22 Needle & e Clip
+Air Adjustment Screw & Spring
+Main Jet #75
+Slow Jet #35
+Top Cover Gasket
+Shaped Float Bowl Gasket
+2 O-Rings

I set the float bowls to the stock height between 21-22mm.
And the needle clip is set on the 3rd notch from the top.

As for points I also got the 4into1.com "Tune Up Kit". Specs from the site are as follows:
  -Kit Includes:
+Oil Filter - Quantity: 1
+Daiichi Points and Condensers - Quantity: 2 points, 2 condensers
+NGK Spark Plugs - Part Number - D8EA - Quantity: 4

Other than those few things, the bike is stock. Its got the original exhaust and as of right now, no air box while diagnosing problems. I will be going back with the original air box/filter set up.

I will send pictures soon as well. Right now I have the carbs off and on the bench trying to redo my 'bench sync'.

Thanks

[flybox1]

Thanks for all the quick responses. This forum really is one of the best!

So for carb rebuild I bought the 4into1.com "Ultimate Carburetor Rebuilt Kit". Specs from the site are as follows:
  -Includes 4 floats with pins, and 4 carburetor rebuild kits. Made in Taiwan.
  -Each Carburetor Kit Includes:
+1.8 Needle Valve & Seat
+D22 Needle & e Clip
+Air Adjustment Screw & Spring
+Main Jet #75
+Slow Jet #35
+Top Cover Gasket
+Shaped Float Bowl Gasket
+2 O-Rings
your jets are garbage you'll need to buy OEM Keihin to get it to tune right  www.jetsrus.com  or reuse your old jets
your float valves will not be the same as OEM, so you will have to use the clear tube method to check bowl fuel level, and adjust accordingly to achieve 3-4mm below the top of the bowl fuel level.  I had to set mine at 24mm to achieve the desired fuel level.   
I set the float bowls to the stock height between 21-22mm. as stated, wont work with aftermarket needles.  clear tube test it
And the needle clip is set on the 3rd notch from the top.  you will want to put back the original needles

As for points I also got the 4into1.com "Tune Up Kit". Specs from the site are as follows:
  -Kit Includes:
+Oil Filter - Quantity: 1
+Daiichi Points and Condensers - Quantity: 2 points, 2 condensers  Garbage...ND or TEC only for points.  this is a known issue.  Daiichis are difficult to time correctly
+NGK Spark Plugs - Part Number - D8EA - Quantity: 4

Other than those few things, the bike is stock. Its got the original exhaust and as of right now, no air box while diagnosing problems. I will be going back with the original air box/filter set up.   YOu cant diagnose anything accurately with the airbox off.  it provides a certain resistance the bike needs to achieve the correct A/F mixture.

I will send pictures soon as well. Right now I have the carbs off and on the bench trying to redo my 'bench sync'.

Thanks

[harisuluv]

That carb kit is probably 80% garbage.  "D22" is a Keyster part number, which just about no one on the forum would recommend.

The float valve and seat I think can be ok, however it doesn't have the exact same dimensions of the OEM type so that means that the 21-22mm float height setting is invalid.

I have fixed carburetors before by removing aftermarket air screws with original OEM ones.

The main and slow jet are probably ok, but not preferred.  Basically you probably only needed about 10% of that kit, and IMO it's a huge waste of money.  Especially if it comes with FLOATS?  How does a synthetic float go bad unless it's been physically damaged?

As far as the tune up kit, I'm pretty sure the Daiichi points parts are extremely ill received with many a horror story on this forum.

Next you are trying to diagnose a problem most likely directly related to mixture (lean) and you're trying to fix it without the air box or any intake at all.  I think you know where I'm going with this.

[flybox1]

Yeah...
So....first step.  Old jets go back in or buy keihins, and put your old needles back in.
Source OEM ND or TEC points (your condensers will probably be fine)
While you are waiting for that stuff to come, fab up a carb stand and an aux fuel source for your workbench.  Something to hold your carbs level while you dial in your float setting so your bowl fuel levels are good.
Once the new parts come, it'll take you no time to install and get the bike started.

If your shaped bowl gaskets swell, and wont stay put in their bowl grooves, they probably are a less desirable compound.
Find shaped ones made of Viton.  They wont swell, and they'll hold up to gas exposure for a long time. 
4into1 has them, cheap.

[brenden.carp]

Again, thanks everyone for the good solid info and for the speedy response!

It is a super bummer to find out that they are crap parts... On the positive side, the bike was a gift to me and the parts in total were only around $150. Ill choose to stay on the positive side of this one now that I have some solid answers haha.

I still have everything I pulled off the old carbs so I will do some cleaning and try putting old back in before ordering new again. If/When I do have to order, I will look into the parts mentioned above.

And yes hairsuluv... I see where you're going. The honest reason behind the last couple times I didn't have the box on was ease of carb removal  It in turn isn't hard to get this air box assembly out so ill continue testing with the box on!

Thanks again to the wealth of knowledge from you guys. I've usually been digging my hands into XS650s that don't usually require as much tenderness as the sohc4's seem to need 

I will be giving updates as I go through the carbs again.

[Deltarider]

Next you are trying to diagnose a problem most likely directly related to mixture (lean) and you're trying to fix it without the air box or any intake at all.  I think you know where I'm going with this.

Question: does that make much difference at rpm near idle?