Topic: 78 550 Stuck at 55

[550Resto]

So here's my predicament...I've got a 78 550 carbs have been rebuilt by harisuluv, new airborne filter, new plugs, 4 into 1 delkevic. She sat for 30 years so its needed se tlc. Only had 9k on the odo and i bought it from my cpusin who purchased it new im 78. I had the points set corretcly, but wanted to bump the advance to 30 degrees where it should be. The issue just recently as the bike was running fine and had power when I twisted the throttle, now it seems like it was good on startup but after she warmed up the idle was soaring in to 4k land and idle and I'd have to adjust the idle screw on the carb to get it to settle down.

I know this isn't correct, but it's the only way to get the idle under control. After I did this she ran like crap. Sounded like she wasn't firing on all cylinders and when I would give her wot she would hesitate and had a backfire or 2. She also wouldn't go above 55 or so.

My question is could this be related to the points/advancer not working correctly? Also as far as the idle goes I've checked for vaccum leaks and none found. Not sure if it could be electrically related? The points are original as is the wires coils and caps.Any help appreciated.

[nicks2319]

I'd put new points on it, new spark plug caps, new plugs, check spark gap, check points gap. Pull off the timing plate and make sure the advancer springs are okay. Verify spark on all four cylinders and check for vacuum leaks and go from there.

[Deltarider]

I'd put new points on it, new spark plug caps, new plugs, check spark gap, check points gap. Pull off the timing plate and make sure the advancer springs are okay

By doing that, you'll have learned nothing. Step by step is best. With only 9K, I reckon your points could still be good.

but wanted to bump the advance to 30 degrees where it should be.

Can you tell us what and how you did this?

[550Resto]

Would it be beneficial to pull the advancer to check the springs and maybe lightly lube it since it was sitting for 30 yrs?

[Deltarider]

The springs will be fine, I'd leave them untouched! but the advancer could have hardened grease inside hampering proper functioning. A timing light will show if it works OK. If you don't have one, you may also take the advancer apart. It's not very hard and you will learn all about the ignition in the process. You may mark by a scratch what the position of the timingplate is now. If possible make pics.

[Lostboy Steve]

I'd put new points on it, new spark plug caps, new plugs, check spark gap, check points gap. Pull off the timing plate and make sure the advancer springs are okay

By doing that, you'll have learned nothing. Step by step is best. With only 9K, I reckon your points could still be good.

but wanted to bump the advance to 30 degrees where it should be.

Can you tell us what and how you did this?

My 550 had 9k on it. Bike was sitting since 91, points looked brand new. Literally Spotless. I'm still using them with HM ignition.

[550Resto]

Yeah, the points actually look decent. I'll attempt to re gap them and get the ignition spot on. Any ideas as far as ignition causing high idle?

[ekpent]

Functioning condensers are important also    Test your exhaust head pipes with a wet rag for a sizzle when warmed up to see if all 4 cylinders are firing or use an infrared temp gauge. Maybe one cylinder is not happy.

[550Resto]

What is the job of the condensers?

[Deltarider]

Two easy checks anyone can do.
Condensors. When idling look for possible arcing. Some tiny sparks are OK.
For clarification see this video.

In this video left condensor (1+4) is bad and causes arcing which means little or no spark at plugs 1+4, right condensor (2+3) shows only very little sparks and is good.
Breakerpoints. Check carefully none of the connectors at the breakerpoints is too close to the plate and so can make ground intermittently when engine vibrates. Failure of a breakerpoint or condensor would affect two cilinders, 1+4 or 2+3.

As far as timing the ignition. With only 9K probably no one has ever moved the timingplates. Consider yourself lucky if this is so. You can then do the timing by just adjusting the breakerpoints. If plates have been moved however, you have to do the complete process: first adjust the breakerpoints and after that you can do the timing by moving the plates. In that order. But I'd start with trying to set the timing by just adjusting the gaps. With only 9K I cannot imagine PO has messed with the plates.

[BomberMann650]

I've was able to cruise beyond 55 with bloo when she had awoke from a 15 year sleep.  Timing wasn't exactly spot on either.

If your timing isn't waaaaayy off (10-15deg off - these aint ford trucks)
May be worth examining other aspects of the bike.

And you did mate the rebuilt carbs to your bike yes?  Sync and A/F mix?

What are the odds you cylinder compression is weak? 

[BomberMann650]

Additional thought.

Did you tell harisluv about the delkevic exhaust?  Iirc those require increasing the jetting.
If you got rebuilt with stock jets you may definitely be running lean.

[Tews19]

Delkevic doesn't need any rejetting acording to the company.

[scottly]

I had the points set corretcly, but wanted to bump the advance to 30 degrees where it should be. The issue just recently as the bike was running fine and had power when I twisted the throttle, now it seems like it was good on startup but after she warmed up the idle was soaring in to 4k land and idle and I'd have to adjust the idle screw on the carb to get it to settle down.

So the bike was running fine until you bumped the timing to 30 degrees "where it should be"? Set the timing back to the "F" mark at idle, where it's supposed to be...