Trying to Figure out my problem.

[suddd123]

2005 RSTD.  Great Bike but having some issues.   Runs good in 1-3 gears and mostly during 4.   When I get to highway speeds and higher rpm in 4 or in 5 overdrive, I am having some issues with the engine not pulling.  I initially wondered if my clutch could be slipping but after riding again, the engine seems to be choking down some when losing some torque.   When I give it lots of throttle during this issue it does pick back up but the torque is still not as expected.   Also it is not uncommon or a backfire during this process.   What do you guys think.  I have recently changed the two back spark plugs but could not get the dog bones off to do the front.   Need to take it to a dealer to help out.   I was having this issue before I changed the spark plugs so the gap and such are correct.  Thoughts.........

 

Edited January 18, 2021 by suddd123

[BlueSky]

Just wild guessing, I suspect it's running on 3 cylinders.  

[M61A1MECH]

What speeds are you at when trying to accelerate in 4th and 5th gears? Remember,  both of those gears are overdrive gears and the Royal Star 4 cylinder likes to make power at higher RPMs, not like a V-Twin at lower RPMs. 

When I had my Venture I was almost never in 4th below 55 or 60 or in 5th below 70. If you crank the throttle open in 4th at around 45 it will bog down every time, similar will happen in 5th around 55. 

With my 98 Royal Star and my Venture I spent a lot of time in 3rd gear.

[saddlebum]

On 1/18/2021 at 6:06 PM, BlueSky said:

Just wild guessing, I suspect it's running on 3 cylinders.  

I have to agree. The thing with these bikes is that they run so well that it is sometimes hard to notice the difference between running on 3 cyl's vs 4 cyl's often only noticeable when you roll on the throttle. Even if your shifting early you should feel some pull even if the engine is lugging but if it is really sluggish then your likely  running on 3 cyl's.

Check your exhaust temps close to the heads and look for  a cold pipe or one cooler than the rest. If your lucky it may just be a bad spark plug, if not then you will need to look deeper. Some possible issues could range from faulty spark  plug, faulty ignition system, bad carb or carb diaphragm or low compression which in turn could be caused by one reason or another.

Edited January 20, 2021 by saddlebum

[BlueSky]

I would also pour a can of seafoam in the gas tank, or a bottle of Gumout with PEA to start some carb cleaning.  

 

[cowpuc]

and if it is hitting on all 4, I would take a serious look at slide diaphrams if it were mine