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R90/6 carb question
R90/6 carb question
Anyone have any idea what might be causing this??
Thanks.
- schrader7032
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Re: R90/6 carb question
Did it just start doing this? Any maintenance event that precedes this?
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
- srankin
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Re: R90/6 carb question
It would help to give the mileage, and last time the valves were adjusted and any kind of tune up was done. Do you still have points or is the bike converted to a pointless system?
The reason I ask and make a point about these things is that carbs should be the last thing to mess with when trouble shooting and airhead. Okay, not helpful but as Kurt mentioned a sticking advance unit can cause the problem. Points wear out and timing changes and that can cause idle RPM changes. Loose or tight valves can cause idle problems. Surprisingly carbs are pretty bullet proof if they get good gas. One of the weak links for them is the cables controlling them. So, on top of the advance system there is a possibility of a cable or cable hanging up.
One of the common problems with carbs is holes or worn diaphragms, your symptoms don't point to this being your problem.
Hope this helps, good luck. St.
Re: R90/6 carb question
Mileage is 72,000. Valves adjusted about 3000 miles ago. Points are practically new, maybe 1000 miles on them. Recently I adjusted the carbs, but just messed around with the adjustment screws to get them in sync.
- schrader7032
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Re: R90/6 carb question
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
- srankin
- Posts: 1081
- Joined: Fri Jul 14, 2017 8:45 pm
- Location: Spencerport, NY USA
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Re: R90/6 carb question
Problem with making carb adjustments other than the cable adjustments is the bike has to be warmed up. Now some bikes warmed up means five minutes or less of running in the garage, for others like My R80RT, it means a two hundred mile ride. I went nuts the first few years of ownership with the bike fiddling with the carbs trying to get things right.
After awhile, I found a lot of the problems I attributed to the carbs were in fact caused by the valve adjustment. Since on my RT, I have the electronic ignition, the ignition system was not a problem. On my old R75 with points, the points, and advance mech could cause problems.
Sorry, I am off track, The trick is, if the advance system is working fine, not binding and the points and timing are fine and adjusted properly, the valves are adjusted properly, then, you have to get the bike warmed up to the proper level to do the carb mixture adjustments. The tricky part is know just how warmed up and just how long the bike can sit at idle while the carbs are adjusted.
I will go back to may original statement, the carbs are pretty bullet proof ONCE they are adjusted for mixture properly, there is little to change in them. Cables and moving parts do change. A sticking cable can cause the problem you are having just as well as a mis adjusted mixture. This sticking cable may not just be on the throttle part of the system but it would be a good idea to check the choke cables and system as well.
At the mileage you have on the bike, have you ever checked the grease in the twist grip? On my bikes, there is an adjustable throttle lock to be used as a crude cruise control, I have inadvertently used mine and forgot to twist them back to loose. Causing the throttle to react slowly when released. Poor grease in the twist grip can do the same thing.
Good luck St.
Re: R90/6 carb question
‘75 R60/6
‘75 R90/6
#therippleride
- schrader7032
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Re: R90/6 carb question
The second thing you could do is to remove the front cover...remove the battery negative connection first...then start the bike. Use the timing light to visualize what the advance weights are doing at idle and all the way up to full advance.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
Re: R90/6 carb question
In other words it no longer races and then dies down and races and then dies down while it's idling.
‘75 R60/6
‘75 R90/6
#therippleride