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S Barker

2024-01-06, 15:48:05
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Varadero 125 low vacuum??

Started by vectrac20tsri, 22/07/21 - 16:00:54

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vectrac20tsri

Hi all new to the forum, recently purchased a 2002 Varadero 125 2002 for £750 which I thought was ok in the current climate.

She's covered 55k miles but seems to ride fine, no loss of coolant or oil but have noticed 1 issue.

The idle fluctuates between 1500 - 1900rpm but no other apparent issues, so decide so spend some money on it including removing the black widow rear pipe as it's way too loud, some front sprockets to mess with, fresh oil and filter and air filter and a cheap set of vacuum gauges to check the carb sync.

Now the rear cylinder shows around 170 -180mm but the front has very little and reading maybe 40 - 50mm, the manual it seems that's the base carb with no adjustment.

Have sprayed wd40 but I can't seem to find a leak, used smoke at very very low pressure and can't see any leaks, all seems to escape via the air filter, Did see a tiny bit from the linkage that joins front and rear carb but was tiny and only noticed it once.

Have done a compression test and I'm getting 190psi rear and 200 psi front, not sure how good / bad this is?  have ordered genuine Honda intake boots just to eliminate it and will clean carbs when they arrive.

Could anyone point me in another direction? bike fires up instantly and apart from the idle it seems fine, the front plug did seem to show a lean condition but it was running a cr9eh instead of a cr8eh so will replace both.

Thanks in advance.

S Barker

I'm not sure if the manual I have is for that particular model but I suspect the procedure is not very different.

The Front cylinder is the base so you adjust the synchronisation to bring the rear cylinder to match it.

As you adjust the synchronisation the vacuum gauge reading for both cylinders will change.



The compression ratio for most models is listed as "11.8 : 1".

11.8 * 14.5 = 171.1 so 190psi or 200psi is a good reading.


I wonder what happen if I click on this - Ooops

vectrac20tsri

Thanks for replying, gonna replace the inlet's and clean both carb's out for good measure and see if there's anything obvious.

From the videos I've seen online the screw seems to only effect the 2nd carb? is this not the case?

vectrac20tsri

Your right mate, I actually got the front cylinder to read higher than the rear but no where near 200 like I have read, probably get the front cylinder to read 150mm which is low? will try different directions.

S Barker


The only values the OEM Honda manual gives are idle speed 1,500 rpm (+-100).
and
Vacuum difference of 4 KPa (30 mm hg)


I don't think it matters what value they are as long as they're balanced and the idle rpm is correct.
I wonder what happen if I click on this - Ooops

vectrac20tsri

removed the tank and all fairings, found both starting enrichment valves just cable tied into the carb, I guess without a seal this is another route for air to enter.

The thread had snapped off the plastic fitting so luckily found them on thingiverse for the African twin.