uncledj Posted September 20, 2009 Share #1 Posted September 20, 2009 I have an 87 Venture Standard, which has been running great, and still runs pretty well, but something's off a bit. It doesn't miss, and seems to run well above 3500 rpm or so, but at lower rpm levels it has a bit of a rumble, as if the carbs are out of sync, but I'm not sure. I run about a quarter can of Seafoam when I fill the gas tank, (most times), and recently replaced the spark plugs, which made no difference. All the plugs looked the same. Someone new to the bike probably wouldn't even notice it, but it's definitley there. Would this be a likely symptom of the carbs being out of sync, or the dreaded diaphragm problem, or could it be ignition? I just can't put my finger on what sort of problem it is. I figure someone here may be able to help clue me in. Thanks. Link to comment Share on other sites More sharing options...
safetyguy Posted September 20, 2009 Share #2 Posted September 20, 2009 I think you need to try the carb sync route as a first step. Link to comment Share on other sites More sharing options...
mbrood Posted September 20, 2009 Share #3 Posted September 20, 2009 Are you idling at 1k? Both carb sync and knowledge of the "health" of the diaphragms are both reasonable maintenance issues to keep up on. My 86 needs a sync about twice a year... they don't drift far but enough to notice on the sync unit to warrant a touch of the screws. If the plugs are looking the same (and flesh brown rather than sooty or whitish) then the majority of the run time is getting the right mixture and burning (firing) all four. Low speed stumbles could be either and the diaphragms are candidates for inspection if you havn't seen them in a while... and for about $100, a sync tool is cheap, it pays for itself after comparing one stop at the shop to let THEM do the 5 minute test... Link to comment Share on other sites More sharing options...
5bikes Posted September 20, 2009 Share #4 Posted September 20, 2009 All 4 have a feeling like being out of sych, or vibration around 3k rpm. They were all sync'ed. Unless serious, don't worry about it. Especially if your getting over 40 mpg. Link to comment Share on other sites More sharing options...
uncledj Posted September 20, 2009 Author Share #5 Posted September 20, 2009 I think I'll need to get a sync tool and take that as a first step. I think I have an old mercury manometer X 4 buried in the garage somewhere, but it also seems that I should pull the diaphrams just to have a look. I guess I'll put it on the winter project list......it's a long list. 69 Chevelle SS needs restored, cb900 custom needs minor restoration, garage needs built, ( Just to house the Chevelle ) wife wants the bathroom redone, need to get the old backhoe sold...and so on and so on. There's no rest for the wicked. Thanks guys (and gals? ) Link to comment Share on other sites More sharing options...
skydoc_17 Posted September 20, 2009 Share #6 Posted September 20, 2009 I am not exactly sure where you are in Ohio, but I have had a few members from Ohio come down to south central Pa. to "my little shop by the creek". If need be I have free overnight lodgeing, the carb. sync. is free and we can take a look at those diaphragms while we are at it. There are a few other things to take a look at and we can do it all while you are here. I keep diaphragms in stock as well as other items that you may need. Let me know if I can help, Earl Link to comment Share on other sites More sharing options...
mbrood Posted September 20, 2009 Share #7 Posted September 20, 2009 Logic says the highest priority is the bathroom... then "she who speaks so loudly" will be happy with most all else. Just my experience... And then Skydoc offers the perfect solution? Link to comment Share on other sites More sharing options...
uncledj Posted September 20, 2009 Author Share #8 Posted September 20, 2009 Skydoc, thanks for the generous offer, I'll keep it in mind. I'm located in Central Ohio, but have a hunting cabin in North Central PA, near a little town called Emporium. Next time I take the bike over that-a-way, I may take the long way around and stop by, (with plenty of advance notice, of course). Again, thanks for the kind offer. Link to comment Share on other sites More sharing options...
Yammer Dan Posted September 20, 2009 Share #9 Posted September 20, 2009 Carb question. Where to look? Lot of good advice here but carbs are on top of the engine just under the Air Box!!! Just had to. I would go with sync on this one. Link to comment Share on other sites More sharing options...
Venturous Randy Posted September 21, 2009 Share #10 Posted September 21, 2009 These bikes are sensative to spark plugs. You can get a set of Autolites at Advance Auto for about $5. I also suggest new spark plug caps. There is a resistor in them that can get corroded. RandyA Link to comment Share on other sites More sharing options...
Pegasus1300 Posted September 21, 2009 Share #11 Posted September 21, 2009 OK since you don't have a sync tool easiest thing for you is to check the diaphragms.Hold them to light and look for pin holes.When you put them back be sure to seat them properly.Next check the vacuum advance unit.I don't have my manual here and its been too long since I did one but someone here can tell you if you don't already know. A bad advance can make it run odd and be difficult to spot.Good luck. BTW I second that previous advice,keep wife happy and all else will fall in place. Link to comment Share on other sites More sharing options...
cimmer Posted September 21, 2009 Share #12 Posted September 21, 2009 One thing to check also is the plugwires and caps. When I replaced mine a while back it did alot to help the low end power. Does take that long and is well worth the effort. A carb sync is always good to do also.. Just my 2 cents worth... Rick F. Link to comment Share on other sites More sharing options...
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