Wishing you all a Merry Christmas and a Happy New Year, ride safe! The CB500Club team

Valve clearance adjustment and Carburettor balance questions.

Share
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Sun 20 May 2018, 3:19 pm

Hello there,

My beloved yellow Bumblebee has recently developed a slight buzz at higher RPMs.

The engine behaviour I'm used to (like most of us I guess) is as follow: quite smooth from 2.5k - 4.5k , then a bit buzzy in the 4.5k-6k range before finally getting in tune all the way to the red line (with a distinctive raging note in this last portion of the rev counter).

Lately, that last portion is as buzzy - if not more - as the 4.5k-6k range, which I find quite annoying.

I disassembled the carbs not so long ago for a good cleaning, new seals and bolts, I haven't balanced them after putting them back on the bike since I wanted to do the valve clearance beforehand (which has probably not been done in 40,000+ km).

So here I am, waiting for some torque wrench to arrive, having studied carefully the workshop and Haynes manuals, with the little apprehension of someone who's never tackled any of these 2 jobs, and with a few questions.

- Regarding the valve clearance: the workshop manuals advises to put some sealant below the head cover gasket around the 2 lobes on each side, do you do that?

- Regarding carb balance: what method do you favour? (Carbtune/homemade hoses/other?) Any advice on making a makeshift fuel tank to be used during the balancing? And if you have a link for the right carb vacuum (brass) screw, that would be helpful. 

Otherwise, any particular advice for these 2 jobs will be appreciated.

Cheers.


Last edited by ZekeVal on Tue 05 Jun 2018, 8:27 pm; edited 2 times in total
avatar
louis_sutton
the 800
the 800

Posts : 258
Location : north london

Re: Valve clearance adjustment and Carburettor balance questions.

Post by louis_sutton on Sun 20 May 2018, 4:39 pm

I use a Morgan carbtune. Never used a fuel tank, it'll run for seven minutes on what's in the bowl, which has always been long enough for me. You need a screwdriver that will reach the adjustment screw though.

I just used a careful smear of gasket silicon, after cleaning the mating surfaces carefully.
avatar
ceejay
the 900
the 900

Posts : 312
Location : Bournemouth

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ceejay on Sun 20 May 2018, 10:04 pm

-I used a bit of generic gasket sealant all the way around the gasket (as its the 19 year old original gasket) focusing on the outside so none ends up in the engine.

-I bought cheapo 'biketec' carb vacuum gauges and a temporary fuel supply holder/thing from both from eBay. They did a good enough job. 

It's fairly straight forward just a bit time consuming in that you can't really order the shims you need until you've opening it all up so is a multi-day process unless you want to put it all back together and take it apart again when the shims arrive.

My advice would be somehow mark the timing chain so it goes back the cams on exactly where it came off to avoid all doubt. There was a topic on here recently about what can happen if it is just a tooth out.

Also I'm sure there is something in the Haynes instructions that is slightly incorrect - unfortunately I can't remember exactly from the top of my head but it is to do with how many degrees it tells you to turn the crankshaft when checking the next set of clearances. However it is fairly obvious if you keep you eye on the position on the cam lobes.
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Mon 21 May 2018, 8:43 am

Thank you for your replies Wink

Do you just put the sealant underneath the gasket (on the engine), or also on top?
avatar
ceejay
the 900
the 900

Posts : 312
Location : Bournemouth

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ceejay on Mon 21 May 2018, 9:36 am

I can't remember which way around but my gasket would have either been stuck the the valve cover or the head so I left it attached on that side and only used the sealant where it came apart if that makes sense!
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Mon 21 May 2018, 9:48 am

Oh ok, it makes perfect sense!

sullivj
the 900
the 900

Posts : 2203
Location : Gatwick

Re: Valve clearance adjustment and Carburettor balance questions.

Post by sullivj on Mon 21 May 2018, 9:06 pm

Don't forget the shim exchange is still running, if you find that you need any.
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Tue 22 May 2018, 4:54 pm

I'm not forgetting that Wink

But to be honest, I was counting on having tighter clearances so that I can try and sand the shims to the correct thickness. Might be a tedious and hard job to keep both faces coplanar, but I'll still give it a go.
avatar
eternally_troubled
Admin
Admin

Awesome!
Posts : 3974
Location : 'ere be fens. (near Cambridge)

Re: Valve clearance adjustment and Carburettor balance questions.

Post by eternally_troubled on Tue 22 May 2018, 11:37 pm

Another vote for Carbtune. A bit expensive though. As mentioned there are other ones that you can use.

I used rather more than a smear of silicone on both sides of the gasket - it sealed fine.

If you get something like a permanent marker or little pot of paint you can make marks on the camchain and cams at strategic points before removing the tension - this can give you a good guide that you've got everything back together correctly. Also it is very worth turning the engine over very carefully a few times before closing everything up, just to make sure.
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Thu 24 May 2018, 8:12 pm

I decided to invest and went for the carbtune.

I'll try to mark the chain as you mentionned, sounds like a good extra safety precaution.
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Sat 02 Jun 2018, 4:54 pm

I received my Carbtune the other day (brilliant piece of kit BTW) and I finally got to balance my carbs this morning. They were not off by much tbh, and I fiddled with the adjusting screw till it seemed better.

I went for a ride this afternoon, and my vibration issue is still there...
It's getting quite irritating, I just don't enjoy riding the bike in that state, and I'm running out of ideas as to what the f*** could be wrong  scratch

I'm summoning the High Council of the Ancients for their much enlightened advices  cheers
avatar
ANDYC
the 900
the 900

Mechanic
Posts : 1006
Location : Windsor

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ANDYC on Sat 02 Jun 2018, 5:52 pm

Are all the engine mounting bolts tight? 
Is the chain too tight? 
Where are you feeling the vibration? 
Is it through the bars/seat/footrest?
The list is endless but we have to start somewhere.
avatar
Crash- Elmit
the 900
the 900

Posts : 277
Location : Rothwell, Nr Kettering

Re: Valve clearance adjustment and Carburettor balance questions.

Post by Crash- Elmit on Sat 02 Jun 2018, 7:26 pm

check wheel balance
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Sat 02 Jun 2018, 8:28 pm

The vibration is a buzz in the entire bike (but I would say mostly felt in the feet), coming from the engine and going stronger as you increase the revs. On top of the actual vibrations, what really strikes me is the different sound compared to the healthy engine sound I've grown to enjoy before.

This can also be experienced in neutral with the bike at a standstill, so no wheel balance or chain issue.

I'll check the engine bolts, sounds like a good starting point.
avatar
ZekeVal
Running out of unique names
Running out of unique names

Posts : 187
Location : Poitiers, France.

Re: Valve clearance adjustment and Carburettor balance questions.

Post by ZekeVal on Tue 05 Jun 2018, 8:26 pm

Upon riding today, stopping on the side of the road with my helmet off and trying to make a video to document my issue, I think I finally found the culprit!

...It was just my right side mirror being loose (the actual mirror in the mirror assembly vibrating like hell as I approached 5k RPM and went beyond). Hope the healthy dose of superglue I sealed it with will do the trick. Impressive how a different noise can trick one's mind into thinking all hell is breaking loose in that engine... 

I'll confirm that next time I ride.

Edit: Confirmed  cheers

Sponsored content

Re: Valve clearance adjustment and Carburettor balance questions.

Post by Sponsored content


    Current date/time is Sun 16 Dec 2018, 6:18 pm