bad miss

New here and new to Yamaha. recently purchased a 96 royal star tour deluxe. I have replaced the plug,s ,oil,filter and cleaned out the carb,s with seafoam. My problem is a mid range shake . When I roll on it seems to run on 3 maybe 2 cylinders. If I run it hard from take-off, it move,s out well Any idea,s as to were to look thanx Doug

You might want to check the diaphragms in the carbs to make sure they don't have pinholes. And make sure the sliders are working freely.

These V4s run surprisingly well on only 3 holes. As well as the above, when I suspect a bunk cyl I do a spit-sizzle downpipe check to see where the fire aint happening. Did the miss just happened after you swapped out the plugs-n-fixins'? If so I would have a peek at the plug caps and where the plug wires exit the coils. Did the bike sit before you got it? Does it have the correct NGK plug/gap?

An infrared thermometer is a great tool to have to check exhaust pipe temps. I think they are as cheap as $20. All 4 should be the same temp is they are working the same.

Maybe a plug wire isn't seated properly

Good Morning All. Yes the bike had sat for a considerable time before I acquired it. I have run seafoam thru the carbs by way of a baster tube hooked into the fuel line and thru the fuel pump. The sliders are working as they should. The plugs aren't stock,but gap is correct. I have a spark tester,but didn't seem to have a brilliant spark on any cylinder. I have an infra-red temp gun and will try that thanx again Doug

If it sat with ethanol tainted fuel in it then it is a possibility (likelihood) that you may have some blockage in the carbs. The low speed circuits are pretty easily blocked up. Also if the carbs are way out of synch then it could run poorly but smooth out as the revs climb but from what your saying my money is on ethanol trouble. Anytime mine sat with ethanol for more than a week or two I had problems that sometimes included pulling carbs to clear things out. If the PO used pure gasoline to store it then you may be alright. I've never wrenched on a gen2 but on my gen1 pulling the carbs is a hassle so I generally check everything else first.

 

Also it will not run properly unless the air filter and air box are all fitted and snugged up, that intake restriction is critical for the CV carbs to work correctly.

I'm the lop eared odd ball varmint around the club who has never really been impressed with Seafoam. I did a bench test with carb cleaners once and Seafoam came in dead last = even after soaking shallacked carb parts for a solid week in pure Seafoam = the stuff did virtually nothing in actually cleaning parts. I have also done the customary Seafoam for storage routine as I know my bikes did seem to run better with Seafoam as a fuel mix but I have even stopped doing that as I have also found a "sheen" on my plugs after running Seafoam that caused my plugs to develop a not so pretty and sharp spark on the plugs. I have also had some not so good experiences thru the years when using any brand but NGK's in my bikes, especially the "D" (small diameter) plugs in my 1st Gens,, this even wayyy worse in running bikes with "C" plugs like found in the little Honda's..

IMHO, if the bike were mine Fulltime, I would start the diagnoses by making sure I had a full tank of fresh fuel in it. I would also check my tank vent as it sounds like its possible that your scoot is running lean as it runs out in R's and is draining the bowls. I would then open the drains on the carbs, cycle the fuel pump a few times to make sure you dont have an intermittent fuel pump issue and to pump the fresh fuel thru the carbs. I would then swap in some normal new NGKS, nothing fancy schmazy - just NGK DPR's. I'd also unscrew the caps, check em over real close for carbon tracking and ohm em out to make sure their spec and clip 1/4 inch on the wires to make sure the caps have a good clean wire to screw back onto. Next I would uncover the battery and check battery connections, hook up my volt meter and check the battery voltage. If that looked good, I would cycle the fuel pump a few times to make sure the bowls are full by cycling the pump to it slowly stops. Move the choke to choke, not touch the throttle, hit the starter and glance down at the volt meter to check the Reg/Stator at idle. As the bike warmed for a few seconds I would begin sneaking the choke off, checking the header tempts in the process to make sure shes hitting on all four. When obvious she's starting to warm up as I drop the choke off (IMHO, the quicker you can get the scoot off choke the better as D plugs dont take to kindly to blackining from over choke) I would tap the throttle and glance at the Volt meter still hooked to the battery to make sure she's jumping to full output as it should be (low voltage across the system can cause exactly the symptons you describe). I'd tap it up off idle a bunch of times watching the voltmeter as I did just to double check output consistency.

Satisfied with all the above, I'd toss the vac gauges on er and check sync, then I would take er out for a test ride and see if she was healed..

Make sense?

New here and new to Yamaha. recently purchased a 96 royal star tour deluxe. I have replaced the plug,s ,oil,filter and cleaned out the carb,s with seafoam. My problem is a mid range shake . When I roll on it seems to run on 3 maybe 2 cylinders. If I run it hard from take-off, it move,s out well Any idea,s as to were to look thanx Doug

sync the carbs sync them again and when you think it's perfect take a 30 min ride and sync them again if you run one out of gas sync them again I've had more and more and more "what's that shake, it sounds great but it runs like a cow in boots""" all noise" do the air box mod shim and Jets then sync again you'll never be happier. Oh did I say sync the carbs.