Borrow carb syncher? [Archive]

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XV8Crisis

18th March 2012, 14:59

Hey guys,

I'm relatively new to bikes, on a reasonably tight budget, so am looking to save some money by doing as much as I believe I can by myself.

My bike pretty certainly needs a carb rebalance, yet I don't have the tool to do so, and at the moment it's outside of my budget to spend the rougly $150 for a one-time job, considering I'll sell the bike within a year (and be looking at dropping more $ on a better bike in roughly the same time...).

Could anyone in the Wellington region let me borrow their sync tool for a weekend job?

My bike is a 1991 CB250FM Honda Jade, but it get more interesting: its history is murky at best, and the bike itself borders on rat. The instrument cluster (amongst other parts... hah) is not original - in fact, I recently figured out that some previous owner got one off of a VTR and that's now what I've got... minus a tachometer. That's right, I shift by ear, and have no idea what my idle speeds are. So in addition to that, I'm probably looking at borrowing a tachometer cluster if anyone has one laying around...

I know it's a long shot, but it's worth a go. In the meantime, I've set out to just clean the carbs and hope it at least improves my symptoms, but it almost undoubtedly won't fix the whole picture, if any of the idling and varying RPM problems. Or shit, barring all the above, I'd love it if someone could balance them for me for some sort of trade! I've heard some can do it by ear.

Many thanks in advance!

unstuck

18th March 2012, 15:04

How about a bit of DIY.<iframe width="560" height="315" src="http://www.youtube.com/embed/2PiQBr20kM8" frameborder="0" allowfullscreen></iframe>:Punk:

XV8Crisis

18th March 2012, 15:15

How about a bit of DIY.<iframe width="560" height="315" src="http://www.youtube.com/embed/2PiQBr20kM8" frameborder="0" allowfullscreen></iframe>:Punk:

Could do, doesn't look too hard. It's a 4-cyl, but as I understand you balance 1 and 2 together first, the 3 and 4, then make sure the 2 pairs are balanced, and away you go.

Cheers

ducatilover

18th March 2012, 15:27

Are your valve clearances in spec? I'd be cleaning the carbs, setting the floats, pilot screws to 2-1/2 turns out etc and then I'd think about synch jobs.

XV8Crisis

18th March 2012, 15:43

Are your valve clearances in spec? I'd be cleaning the carbs, setting the floats, pilot screws to 2-1/2 turns out etc and then I'd think about synch jobs.

Not sure yet - am looking at cleaning the carbs here in a few hours. Not 100% sure what the specs are for my bike as I don't have the manual and the only manual is in Japanese, but if my logic is right then since it's the exact same engine as a CBR250, albeit tuned a bit higher, then I can use the valve clearance, float, and idle speed specs for the carbs. I have a CBR250 manual.

ducatilover

18th March 2012, 15:47

Not sure yet - am looking at cleaning the carbs here in a few hours. Not 100% sure what the specs are for my bike as I don't have the manual and the only manual is in Japanese, but if my logic is right then since it's the exact same engine as a CBR250, albeit tuned a bit higher, then I can use the valve clearance, float, and idle speed specs for the carbs. I have a CBR250 manual.
Should be similar specs to the MC17/19 CBR250 for the carbs. From memory the CB250 Jade made less power (softer cam profiles, diff ignition and lower compression) but I imagine the float heights are the same if you have the same carbs.

If you're having horrid rough idle issues it might pay to check the intake rubbers and vacuum lines.

XV8Crisis

18th March 2012, 16:18

And when you're talking about valve clearances, are you talking about the guillotine and butterfly valves in the carbs, or the cam valves in the engine?

ducatilover

18th March 2012, 16:45

And when you're talking about valve clearances, are you talking about the guillotine and butterfly valves in the carbs, or the cam valves in the engine?
The cam to valve clearance in the motor.
The butterflies in the carbs are set when you sync them (that's what the sync does)
There's no point doing a carb sync if you haven't checked your valve clearances, the CBR250 manual should be a big help there, not a hard job, just requires careful thinking and it pays to double and triple check everything. :yes:

nzvlogger

18th March 2012, 17:16

lol that carb sync thing is awesome, im gonna try that! You could probably just hook up 4 bottles i guess?

XV8Crisis

18th March 2012, 17:39

Aw man, seriously? I was hoping to not mess with the engine at all. Checking cam valves clearances sounds like a careful, serious job! And it's a 4 cyl... That's definitely a different weekend and a whole lot of self encouragement...

lol that carb sync thing is awesome, im gonna try that! You could probably just hook up 4 bottles i guess?

Yea but wouldn't you have to have tubes running from each bottle to every other bottle? In the vid he's using rubber stoppers from what looks like a science kit/supply, which is ideal, but... other ways of jimmying it? Punctured rubber diaphragm or foam? That's sorta what I meant with the balancing carb 1 and 2, then 3 and 4, then rigging it up right to measure the pairs in balance.

ducatilover

18th March 2012, 17:42

Aw man, seriously? I was hoping to not mess with the engine at all. Checking cam valves clearances sounds like a careful, serious job! And it's a 4 cyl... That's definitely a different weekend and a whole lot of self encouragement...

Worth doing it though :yes: has always made my bikes happier (probably because none had any history of real work...:laugh:)

XV8Crisis

18th March 2012, 18:10

ducatilover

18th March 2012, 18:13

And with the states of my bike in general... ugh. Not looking pretty.

I mean, that's 16 valves, and to get to those (to even just inspect valve clearance!) I need to remove the cylinder head, which starts to get serious. Beyond that, if they do actually need adjustment, the CBR engine uses shims... meaning I have to get the valve cover off... all very internal, careful, serious, clean, organized, tender work...

I'm scared. :shit: and don't wanna...

I'll just pray that everything works well enough after a carb clean and idle speed adjustment, right?

Yea, right... hah.

No cylinder head removal.
Just under the valve cover.

Valve cover off, measure clearances, pull cams out, pull buckets out, record shim sizes, work out what new sizes you need, put new shims in, cams etc etc, done.

I tend to at least double check all clearances before pulling the cams out.

nzvlogger

18th March 2012, 18:54

It should be fairly easy really if you have a service manual just follow the instructions :D it sounds worse than it is

unstuck

18th March 2012, 20:00

Well heres one for 4 carbs, and you can drink it too.
<iframe width="420" height="315" src="http://www.youtube.com/embed/ubV9Xvk0U_Q" frameborder="0" allowfullscreen></iframe>:sweatdrop

unstuck

19th March 2012, 07:09

If you are serious about working on your own bike, then this may be handy. http://www.dansmc.com/mc_repaircourse.htm :Punk::Punk:

ducatilover

19th March 2012, 11:31

If you are serious about working on your own bike, then this may be handy. http://www.dansmc.com/mc_repaircourse.htm :Punk::Punk:

Very helpful website that one :yes:

Laava

19th March 2012, 12:13

FWIW many years ago I bought a set of 4 vacuum guages to do sync work. Useless! They all are slightly differently calibrated making it impossible to get anything accurate. The manometer works way better and is 100% accurate. But you need to be sure you have good and proper spark, timing, float levels and clean carbs before you start with it. So it can be a labour intensive job. But rewarding when you get the results.