Gen 1 Missing and Stumbling

[RossKean]

I don't think I would hang my hat on the two inboard cylinders running 100° hotter. (Measured at the top of the cylinder or exhaust?)

The difference isn't all that high, accurate measurements are difficult to make (depends on exact point location) and I would expect the inboard cylinders to be slightly warmer anyway.

I would start with the throttle position sensor and the big connector under the tank.

 

[SkooterG]

First things first..... Idle speed.

 

[japperman]

Update.

I just plugged off the PAIR system. I also checked all four plugs and they are showing rich/missing (black dry residue). The temperature difference did not change. Outside pipes are at 250 and inside are at over 500. That is at idle and off idle the temp difference stays. I really expected the inner two plugs to be normal..... I am going to give the connector another cleaning but it will be mid week. Idle is slightly over 1000 rpm. I will also check with dealer to see if TPS has been changed.

Thanks all.

Jasper

 

[Ignacio]

Idle is slightly over 1000 rpm. I will also.....

Then that's not right. Fix it as first suggested and courteously reminded! That Skooterg knows his FJRs.

 

[mech 1 twa]

1 and 4 share the same coil. 1 is up on stroke 4 is down. Wasted spark system both plus fire at the same time. Slight popping at cold idle is a known issue but should not mis-fire. under load.

Tight valve will be worse when cold. Head expands more than valve increasing clearance and may go away when hot. BUT it will cause a valve to burn someday.

 

[Bustanut joker]

Ok I'm kinda confused here.. I thought the temperature differential was 100. Now it's 250?

I'm still thinking coil or injectors. Granted there aren't many instances of coil failure, it can and does happen once in awhile.

 

[RossKean]

...and the idle went from 1100 to slightly over 1000. Set the idle up a bit higher and check for the TPS recall. (as well as the big connector condition)

I have used an IR temperature gun to try to measure pipe temperatures. It is almost impossible to get a good reading shooting around cowling, radiator etc. The laser "spot" on the gun is really misleading - it is really measuring a much wider area instead of just at the laser dot. I spent some time chasing a perceived problem when the (erroneous) readings I made with the IR gun were suggesting a fueling issue. I did have a problem but it had nothing to do with cylinders getting different amounts of fuel or spark.

Don't take plug "readings" too far. They may be indicative of what happened in the last couple of minutes - not general behavior over an extended period of time (especially a dry carbon deposit). You could have a fuel injector issue but I'm certainly cot convinced; same with coils.

 

[John d]

I had a somewhat similar situation on my gen2. Read this link and see if it helps

 

[audiowize]

Please do check the cam/crank timing. Having things off a tooth or two will still allow the engine to run, but with lumpy power and sometimes an unusual idle.

As has been suggested previously, it's not unreasonable to check for spark just to be sure that isn't the issue.

You might also want to check for vacuum leaks around the intake boots and all the vacuum lines/ caps. You may have a lean or rich pair of cylinders just based on a cracked hose. I use a propane torch (not lit obviously) to dribble propane around the hoses and seals with the engine running. If the RPMs wander when you hit a certain spot, that's a good indicator of a leak.

 

[japperman]

Update.

Took bike to local dealer and they:

Replaced spark plugs

Replaced TPS

Cleaned injectors

and it still runs the same. (they gave up).

It doesn't have any gunky goo in the map sensor vacuum lines.

I also increased the idle as one member suggested, but with no difference.

I purchased a Motion Pro sync tool and synced the throttle bodies. No change.

So I brought it back home and have removed the valve and side engine cover, and the valve timing is spot on.

My next step is to check valve clearance and then do a compression test.

(getting the valve cover back on is going to be fun)!.

Will advise

 

[japperman]

I couldn't stand it so I went ahead and checked the valve clearance.

Exhaust was fine (20 to 22 mm).

Intake was another story.

#1 both valves were at 11mm. 10mm would go but 12mm will not.

#2 and #4 are at a tight 15mm. #3 was a easy 15mm but 17mm would not go.

Taking off the cams now so I can order some shims.

 

[JoshHefnerX]

Any update to this?

 

[japperman]

All,

Sorry for the delay but I have been riding the bike! After the valve adjustment, the bike starts and runs like new. No hesitation, no missing and it hums out the exhaust. The tight #1 intake valves were the problem. I checked compression afterwards hoping that the valves were not burnt, and to my surprise the #1 cyl was 5 lbs higher compression than the other three. I guess there might be some carbon buildup? All of the plugs look the normal tan color now as well. Extremely happy with the results. I went ahead and also put a Rostra cruise on it which is working perfect. Have been to Arkansas to ride twisties and down to COTA for MOTOGP and it even runs well through heavy rain! Love the bike. My next purchase is a more comfortable seat and I am going to relocate a power outlet to an easier place to reach.

Thanks to all for your assistance.

Jasper

 

[AuroraTom]

All,
Sorry for the delay but I have been riding the bike! After the valve adjustment, the bike starts and runs like new. No hesitation, no missing and it hums out the exhaust. The tight #1 intake valves were the problem. I checked compression afterwards hoping that the valves were not burnt, and to my surprise the #1 cyl was 5 lbs higher compression than the other three. I guess there might be some carbon buildup? All of the plugs look the normal tan color now as well. Extremely happy with the results. I went ahead and also put a Rostra cruise on it which is working perfect. Have been to Arkansas to ride twisties and down to COTA for MOTOGP and it even runs well through heavy rain! Love the bike. My next purchase is a more comfortable seat and I am going to relocate a power outlet to an easier place to reach.

Thanks to all for your assistance.

Jasper

Jasper,

I'm glad your bike is now running properly but I disagree with your conclusion that problem was tight valve(s).

.11 mm is slightly over .004 inch. That is out of spec but would not cause the problems you originally described. My "guess" is that one or both cams were a tooth off and were put back correctly after the valve adjustment.

Tom

2004 ABS

McCruise

10:33 final drive

 

[SkooterG]

Agreed. Slightly tight valves were not the cause of your problems. Glad it is fixed however.

 

[FJRBluesman]

My guess... Your battery terminal(s) were loose. After removing them and taking apart your valve cover etc you bolted it all back up nice and tight. Check the positive terminal for excess rubber pinched between the terminal and battery post, cut it away and it won't happen again. Trust me on this one.

Link1

Link2

 

[japperman]

Regarding the comment about "valve timing being the cause of the problem".

After I brought the intake valve clearances back into spec, the intake cam was off one tooth.

But I was not sure if it was like that prior to the cam removal, or if I had done it.

Thanks.

Jasper