misfire

[geniusloerts]

#4 on the frakinbike is having misfire problems. the exaust pipe temp is not getting as hot as the others its around 109 degrees the others are twice that. the carb is clean, the plug is working, the coil checks out, even the compression is good its higher than all the rest..... what is going on? If i unplug the #4 wire it almost kills the engine, but why isnt that cylnder not getting as hot as the others? when you accelerate the motor number four starts to pop and back fire.

[dbeardslee]

When is the last time you synced your carbs? Also, on pulling the plug wire, my understanding of how the coils work on these things is that the electrical pulse makes a circuit from one coil wire to the other so if you just pull the wire you're probably killing two cylinders unless you ground it to the engine with a plug in it. Might check the resistance on your #4 cap too. Just some thoughts.

[DGXSER]

I'm with Doug, it is either carb related, or the wire/cap to no 4 has a short of some sort. Having one plug wire loose will cause all kinds of issues with rough running DAMHIK. It definitely needs both plugged in.

[XJOK2PLAY]

geniusloerts,

Forgive me, but I don't recall the story on the Frankinbike...

Is it a mix of years & parts? Hence the name?

It might help to know a little more...

But, the previous advice sure sounds like a good place to start, too.

If the problem's still unresolved after checking those things, give us a few more details.

[geniusloerts]

did the ground test with a 5th plug and it didnt make a diffrence still ran the same.

checked the pick up wires, there didnt apear to be any loose connections or broken/cracked wire.

I still have the random backfire through the carb...


as far as being a frankin bike i think it is just body parts...this is my brothers bike, i remember him saying that it was put together from parts, but im not sure about the electronics and motor/ carbs

[dbeardslee]

And the last time you synced was...? Also, have you run the resistance tests on your ignition coils and plug caps? I didn't see any mention of it in your signature, so I'm assuming your running the stock coils and wires.

[geniusloerts]

I'm not sure the last time my brother did a sync, the last time he did do it, it was just a bench sync.

we did check the coils and they are fine.

[trbig]

It sound slike #4 is flooding out to me. And, although a bench synch should get it close enough to run to be able to properly synch it, I wouldn't stick with only that. All the cylinders draw differently.

So, even though the carb may be clean, you may need to check the float height and that the float valve is seating. If the bike has an octo that is working, you won't know if you have a bad float valve with the bike off. Even possibly a sinking float depending on carb year.


Tod

[dbeardslee]

Sounds like it's time to buy your brother some beer and get him back over with a sync guage. A proper sync is something that IMHO should be done at least annually. One of the symptoms you can get with out of sync carbs is backfiring through the carbs. I'm in no way disagreeing with Tod - he may be right. I just like to do the easiest stuff first .

[ridingagn]

I'll start by saying I'm working on the bike with geniusloerts. It's easier for me to chime in here than to have him pass along what I ask while he's working on other stuff.
Here's more details.

The bike was running perfect (of course, don't they all?)
The bike started running badly and would die when hot unless choke was on first stage
Drained tank, put in fresh gas and 1/3 can Sea Foam. Ran for 30 miles.
#4 plug was fluffy black, all others light tan
4 new stock plugs installed.
1/4 coil tested high ohms on primary and secondary, so it was changed out with a spare 1/4 coil that is within spec.
#1 and #4 plug wires switched.... still runs rough.
# 4 header idles at 105 degrees, #1,2,3 idle in 140 range.
# 4 puffs back through carb randomly at idle, backfires randomly at 3,000 rpm
WD 40 check indicated no intake leaks.

At this point I'm leaning toward sunk #4 float, although there is no indication of excess gas (overflow, dripping, smell etc.)
Help!

[ridingagn]

Sounds like it's time to buy your brother some beer and get him back over with a sync guage. A proper sync is something that IMHO should be done at least annually. One of the symptoms you can get with out of sync carbs is backfiring through the carbs. I'm in no way disagreeing with Tod - he may be right. I just like to do the easiest stuff first .

You are probably right. I have a quad sync, so I'll do that before I remove the carbs again to check floats.
Thanks,
The Dad

[ridingagn]

Sounds like it's time to buy your brother some beer and get him back over with a sync guage. A proper sync is something that IMHO should be done at least annually. One of the symptoms you can get with out of sync carbs is backfiring through the carbs. I'm in no way disagreeing with Tod - he may be right. I just like to do the easiest stuff first .

Okay.... I synced carbs per Clymar. All four reading exactly 12hg at 1000 rpm.
Bike still idles rough, like on 3 cyls and stumbles on accl. Pops back through carb #4 randomly and especially when giving throttle.
No apparent change. After sync running for about 4 mins at 1,000 with spikes to 3,000rpm, headers #1,2,3,are running at 210 degrees, #4 is at 110 degrees.
There is no top end noise, no shim clatter, ect.
All agree float check is next?
Thanks again guys for all the help. We'll get this sooner or later.
Papaloerts

[XSokieSPECIAL]

Okay.... I synced carbs per Clymar. All four reading exactly 12hg at 1000 rpm.
Bike still idles rough, like on 3 cyls and stumbles on accl. Pops back through carb #4 randomly and especially when giving throttle.
No apparent change. After sync running for about 4 mins at 1,000 with spikes to 3,000rpm, headers #1,2,3,are running at 210 degrees, #4 is at 110 degrees.
There is no top end noise, no shim clatter, ect.
All agree float check is next?
Thanks again guys for all the help. We'll get this sooner or later.
Papaloerts

Check the float level for sure, but if it's # 4 you should be able to pull the bowl without removing the rack. Check the pilot jet if you can get it removed because if its missing at idle for lack of fuel either the pilot jet is plugged or you have a broken off idle mixture screw tip.

$.02

[jjwaller]

Float level and operation, yes. Check it.
Low speed circuit. More probable.
Remember on these carbs, that there are 2 itty-bitty tubes(?) in the roof
of the carb bodies. There are three, but one is for choke. (I think)
Real easy for one of these to be clogged a bit. With the modern gas(crap)
every little bit matters.
Anyway, make sure the entire low-speed circuit is clean.

[DiverRay]

OK, since no one wants to try something else, it's my turn!
Check the valve clearance and timing chain tension. The valves on the XS1100 CLOSE after a while. You may not have the valve fully closed, so it can't fire properly. This will also show up on a compression test as a low cyl.
Again, we don't have all the facts, how many miles since the last valve check, etc.
Just my $0.02, and worth every penny!