1988 Royale not wanting to idle correctly and stalls out at higher rev

[van avery]

Picked up a really nice looking 88 Royale this week and haven't had much time to work on it yet.

Won't idle consistently and needs about 1/2 choke. Put about 1/2 tank of gas and can of Seafoam in her and ran a bit to get into the carbs and then let her sit a couple of days. Took out for very short ride and started out with plenty of power then about a quarter of a mile it started to bog down like running out of gas when I let off it, dropped back and recovers. Does the same thing if I keep it rev'ed up sitting on the center stand. I was not hearing the fuel pump when I turned on the key so I pulled the discharge line and hit the key and it spirted nicely.

Last owner said he had someone clean the carbs and was still having problems so wanted to sell.

They have taped off about half of the air filter inlet and it makes a difference if you start pulling it off. (guess this is a poorman's choke)

I did check one carb this afternoon and at least the left rear float seem to be set correctly. The brass plugs on the idle mix screws were removed and that carb was turned out 3 and 1/4 turns. Pulled the air filter with it running and all the sliders seem to be bouncing nicely. Have not tried to sync the carbs yet. Sprayed starting fluid are carbs and it didn't make much difference. Looks like new air filter.

Before I pull the carbs is there something else I should check?

[Flyinfool]

First thing is when you start it cold. check to see if all the headers are heating up at the same rate. A cold one or two will tell you which cylinders are not running. Once you have that narrowed down then we can start figuring out why they aren't running.

[BlueSky]

Last Christmas I noticed that Radio Shack had little sensors for $20 that could be used to read the exhaust pipes temperatures. Would be handy. If they are still in business.

 

I wouldn't sync the carbs until I was sure all of the cylinders are firing correctly. You would just muck it up.

[KIC]

I would also check the diaphragms and make sure that they are in good condition and also that when they were installed it was seated correctly. I had an issue with mine when I thought i was seating them correctly but at the last millisecond when I couldn't see, they would bind just a little and create a leak. I used a small screw driver to hold them in place until the cap was flat and tight. Just a thought.

 

Actually another thought is that there is an other Diaphragm in the front part of the carbs that is rarely talked about. It is a long square one. When I was troubleshooting a serious carburetion problem on my 87, and I finally for the carburetors apart, I found that the previous owner had use some type of cleaning solution that destroyed those square diaphragms and my bike with not run above all fast idle and always seem to be choking out or running out of gas because those diaphragms fried.

[van avery]

I'm working on a set of carbs on an 85 royale project now so haven't had much time to work on the 88. Will check the main diraphams. Not sure about the square ones your talking about. I know about the small round ones part number 3LD-1490H-00-00 in cheap cycle parts ( I believe they are to aid in stopping the popping on deceleration), and yes I have seem those pretty chewed up before. Just got new battery to replace in the IR temperature indicator so have not checked that yet.

Problem is too many project bikes (3 now 78 KZ1000, 85 and 88 Royales) and the truck started giving me problems this week end.

Been running can of Seafoam and half tank of gas and letting it idle while working other things and at least I can rev it up around 5000 rpm and hold it there without it acting like its running out of gas but I still have to have half choke to keep running. Have removed half of the tape PO had blocking the intake horn so it is running better. Most likely still going to have to remove and clean the carbs. PO said he just had that done about a month ago. But then again how clean is clean.

Thanks for the ideas..... now if I can find some extra time.

[van avery]

Finally got some time to work on the bike last night and today.

Found bad plug front right cylinder. Bought new set of plugs today and replaced all. Finally got it to hold at 1000 RPM without choke but idle screw is almost at top limit.

Did several other checks today and finally got her to idle at around 100 RPM ( without additional tape on the inlet horn)

Need to check temps after a minute yet but while doing other things after running about 10 -15 minutes cylinder temps were. 1. 184 2. 219 3. 229 4. 185

Idle mix screws 1. 3 1/8 turn out 2. Was shut hard have opened to 2 3/4 turn 3. 3 turns 4. 2 1/2 turns

No real response to starting fluid around intake and carbs.

Put carbtune on it and basically had no vacuum showing. Switched to gauges and get approximately 1" vac at 1000 RPM and if I rev it to 4000RPM I only get about 2" of vac. Seems like I should be getting around 9" vac if I remember correctly.

I should do a compression check but ran out of time right now.

Ideas?

[cowpuc]

I would pull air box cover and filter, check the slides for ease of movement. I would also still pull the the slide diaphrams , take a peek to be sure all is well in there - make sure they are all lined up and sealed properly. By all means, doing a compression test just to be sure all 4 are adequate is always a plus when diagnosing a scoot you really have no idea where its at..

[van avery]

Well got back to the bike this afternoon.

The right rear (3) was cooler than the rest so tried to do the shotgun clean method but the idle mix screw would not pop out. So sprayed carb cleaner in both ways through the idle circuit and put thing back together and did compression test and found 1 ,3 and 4 all at 140 PSI but number 2 (Left front) only showed 20 psi. Went back and rechecked again and still got 20 PSI so put a little oil in it and it only went up to 30 PSI. So started to remove the valve cover and I'll check the front valves for clearance. Hope that's it????

Did get her started with the Air filter off and full choke and the sliders all bounce around nicely. Diaphragm on number 3 looks almost new.

[BlueSky]

If you have to drill out that idle mix screw, new ones are still available at partzilla.

[van avery]

The idle mix screw would unscrew but the procedure said to get it out I needed to air blow through the pilot jet hole in the intake and it should just pop out. It would not.

Might still have to pull the carbs but I'm going to try valve adjust first.

If I remember correctly a couple years ago I had and 83 venture that basically was doing the same thing and once I did the valve adjustment the problem with low vacuum got much better.

[BlueSky]

When I removed my idle mix screws, I put a touch of sticky gasket sealer on the end of my screwdriver and touched the screw and pulled it out. Then I used a pick with a slightly curved end to pull the tiny washer, o-ring, and spring out.

[van avery]

Thanks for the suggestion. Borrowed a valve shim kit this evening. Now just have to get back to it.

[van avery]

Had some health problems since starting this but finally got back on it in short periods.

Finally found that the intake valves on number 2 cylinder were carboned up and not sealing. Had very low compression on that cylinder. Hooked up air line to the hose on the compression tester and had real good air flow back thru the carb. Pulled front head and lapped the valves and then treated the rings with some marvel mystery oil and the compression came much back up. I still was not getting heat on the exhaust pipe #2 , and very low vacuum when trying to sync carbs. So pulled carbs and cleaned (PO had them professionally cleaned) and I found two carbs had the idle jets plugged. While there I replaced the o rings under the intake boots. Runs much better now.

Now I’ve got to work on the tail light indicator, comes on when I use the brakes. The cruise control won’t set and the CB turns on but I don’t hear it transmit, and the throttle doesn’t return as it should.

[bongobobny]

Yah!! Sometimes "Professional" carb work is pure crap!! Lots of people out there that THINK they know what they are doing!!

 

Tail light indicator may be as simple as a bulb filament burned out! On the MK1's, the tail light had 2 dual filament bulbs, and if one of the filaments burned out the other would still light up, but the fault indicator might come on. Also check to see if anybody installed LED bulbs, they do not draw enough current and cause the fault to light...

[van avery]

You were right, the rear bulbs were replaced with LEDS.

Found short in the wiring for the rear running lights (PO) had pushed wire together and then used shrink wrap just before fuse connection.

Throttle cable was frayed on the small pull cable to the carbs. Have one on order. I believe that was the problem with the cruise control too.

[bongobobny]

Cool!!