Quick question

I am frustrated with my bike's idling. I have recently cleaned and synced the carbs,c hanged plugs, checked valves and cleaned air filter.

After re-assembling everything I have been struggling to set my idle speed.

Once the bike is warmed up, when I come to a stop the idle will quickly come down to about 1500-1600 rpm and over the course of 30-60 seconds dip back down to about 1100 rpm. If I set it lower, the bike will often stall. The idle is also a bit "lopy" as it fluctuates between 1k and 1200rpms.

What have I screwed up? Maybe I need to re-check the sync?

This has always been a bit of an issue on this bike, but it seems worse since I have cleaned everything up (the bike runs better and smoother in all other conditions). I have not touched the air mixture screws nor have I moved the carb needles.

Could be a vacuum leak. Or not.


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I think that's the standard answer for these symptoms.  Check all of the vacuum lines, especially near the nipples, for cracks.  It's cheap to replace vacuum lines...

Ciao,

From memory, there are two plugs on the rear cylinder ports, and two line on the front cylinder ports for the pairs crap. What other vacuum lines are there?
Are the ports that connect the pairs system back to the air box considered part of the vacuum system?

This may be a good excuse to de-pair the thing. I just need to find some block off plates for the cylinders and some plugs for the front cylinder vacuum ports.


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 Block off plates

http://m.ebay.com/itm/Honda-VFR-750-VFR750-Interceptor-Exhaust-Emissions-Plate-AIS-Smog-Block-Off-Kit-/232139921877?nav=SEARCH

Items 6 and 18 are what you need for the ports with the small hoses(Where you attached to sync the carbs).

http://www.partzilla.com/parts/search/Honda/Motorcycle/1994/VFR750F+A/REAR+CYLINDER+HEAD/parts.html

For the ports on the airbox you just need a couple rubber caps the right size.

I had good luck with these:

https://tpoparts.com/cat093/index.php?route=product/product&keyword=S-0062&category_id=0&product_id=53

Can't remember if the rubber caps that they included fit the airbox though.

Yeah and when you replace those vac lines i'd go ahead and resync after.

Did you check/adjust your valves? That shouldn't cause your intermittent issues, but IMO when you've got it all apart for the 2nd/3rd time i'm one for starting a fresh job to make it feel like i'm getting something new done as well. It'd be like if i had to put my shoes on 3 times, maybe the 3rd time i'd change socks or something just to make it feel worthwhile hehehe

Also while you've got the fairings off check the stator connector. Poor charging can cause the weirdest issues. 

Thanks for the links guys. The TPO guys are out of stock of the VFR kit so I ordered on ebay.

atx: thanks for the tips. I did check the valves (all in speck) while I was in there. Also replaced the plugs, cleaned air filter. I have a voltmeter mounted on the triple tee to monitor charging voltage to the battery - no issues there.

Update: what a pain it was to get to the rear cylinders! But I got it all done and re synced the carbs. It's better but when coming to a stop the idle is still a bit high by 300-500 rooms and very slowly drops down to its setting.
It's manageable and I may try another sync once the burns heal on my forearms...


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