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Discussion Starter #1
Prelude:
A couple weeks ago, just after leaving a fuel station, my 95 Daytona 1200 started an erratic misfire, and completely died on the freeway(think: a low gas tank feel).

After letting her cool down, she started right back up, but was running rough, as if she were choked for fuel. Holding her to 5k rpm, she would spit and sputter horribly. Rotating the petc0ck to R did nothing, and rotating it to P helped ever so slightly; However, the warmer she got, the worse she ran.

Short of pulling the carbs to replace the witches hats and air filter(which were both done 5k miles ago), the handy-dandy search tool on this fantastic site pointed at possibly:

  • Cracked or kinked vacuum hose,
  • Cracked vacuum cap(s),
  • Bad ignition coil(s)-or coil connection,
  • Bad ignition sensor.
I figured my best approach would be to:

  • Empty, then clean the fuel tank, and fuel cap.
  • Empty carburetor bowls.
  • Disassemble, then clean the petc0ck.
  • Replace vacuum caps, and line, (sleeving the tight line bend with steel braiding).
  • Replace spark plugs-(Had DPR9EA-9 installed 5k miles ago at my last valve job. BAP GEON only had DPR8EA-9, so that is what I used). Pulled plugs were evenly tanned across the head.
  • Clean/crimp terminals, and replace both ignition coils with Nology.
  • Replace ignition sensor (Mechanic @ dealership said 1mm gap?).
Now:
Upon completion, I filled the fuel lines with a little techron/gasoline mixture, and she fired right-up. I let her idle for about 10minutes, in an effort to cleanse any water/junk from the idle circuit, had bad gasoline been culprit. I then ran her around town and down the freeway for about an hour last night, before parking her in the garage. She still had a light sputtering issue at steady throttle, but it had shifted to roughly 6k rpm.

The temperature this morning was about (5C) 40F. I went outside and using full choke, fired her up. She ran fine, and after about a minute or two, I backed the choke off.

Getting ready to leave the drive, I shift her to 1st gear, not realizing the side stand was still down. She cut-off, so I raise the side stand and try to start her...No go. She stumbled like she was about to start, then nothing. Using the choke, I then try to start her...Nothing...I back the choke off and try again-and POW!!! A really loud backfire. Last chance, I try again with a half choke, and nothing, except for an awful noise from the starter clutch when I let off the start button.

I think the initial Techron/gasoline mixture ratio may have been a little too close, thereby fouling the plugs. So, I'll likely go out and get some more today.

Is there any great difference between DPR8EA and DPR9EA?

Trusting the Triumph mechanic, I am using a 1mm gap on my ignition pickup. Was I incorrect to use this gap?

Could all this just be attributed to the idle circuit on my Mikuni's going South?

Any ideas y'all are willing to pitch would be greatly appreciated, as I have Shriner's rides this Friday and Saturday.
 

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Man, you've done almost everything. The only thing that I can think of is that the o-ring seats for the float needle valves go bad in Mikunis, requiring replacement. You might also replace the fuel lines while the carbs are out.
 

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Discussion Starter #3
I will pull and pitch the new plugs, after a thorough inspection. I just hope I didn't trash my sprag this morning.

The gap on my new Gil pickup coil is 1mm. The PVL I pitched was 0.8mm. Do you happen to know what the Hayne's Manual states as correct?

As far as carburetors: I'm half tempted to buy and rebuild a set of Mikuni's for standby.
 

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I will pull and pitch the new plugs, after a thorough inspection. I just hope I didn't trash my sprag this morning.

The gap on my new Gil pickup coil is 1mm. The PVL I pitched was 0.8mm. Do you happen to know what the Hayne's Manual states as correct?

As far as carburetors: I'm half tempted to buy and rebuild a set of Mikuni's for standby.
Haynes says 0.6 to 0.8 mm on the pick-up coil air gap.

If you're going to hunt for another set of carbs, I suggest looking for a set of Keihins. They have fewer problems and give better fuel economy. I don't think that much, if anything, needs to be changed from the Mikuni setup.
 

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I'm a newbie on this forum. I've got a 95 Sprint with 40k on it with no problems at all.But enough about me. It seems you've covered most of the possibilites but I must ask,Did you refill the tank with fresh fuel? I've gotten fuel that was barely combustible before. In an effort to reduce water contamination alcohol is sometimes added to the tanks and if you get some of the mix from a low tank it will barely burn. If you smell the gas it should have a pretty sharp odor and evaporate pretty quick if you spill a bit and blow on it. I chased the same problem on a friends Kawasaki and still kick myself occasionally.If it isn't the fuel I would pull the float bowls and clean the jets and idle circuits.Could be some contamination.
 

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Discussion Starter #6
So Far...

If the following post results in disjoined rambling...My apology as I'm only running on a few hours sleep.

Before I begin, here are a few questions that any information on will be greatly appreciated:

Do any of y'all have the TDC location for Cyl 4 scribed on the metal wheel?

Are all igniter wheels adjustable? Mine is slotted, with set screws and 5 setting-lines.

Although GREATLY diminished, I still notice this: While steadily holding 5000rpm, there is what sounds like erratic popping, similar to the way an exhaust leak sounds. If there is surging, it is very slight. Also, I cannot locate any areas in my exhaust that appear to be leaking. Any ideas?



1.) Changed plugs. The ones in the bike only had 300 miles:
  • Cyl 4: Piston top shiny. Plug=tan.
  • Cyl 3: Piston top slightly damp with a light carbon film. Plug=tan.
  • Cyl 2: Piston top wet and thicker carbon film, partially dissolved(came off easily with a cotton swab). Plug=lightly black and wet. Torque was noticeably less on plug removal as well.
  • Cyl 1: Piston top and plug, similar to Cyl 2. Torque on plug was o.k. though.
  • The new plug tops were coated with di-electric grease, and the new PVL sparkplug wires were snapped into place.

2.) Crimp connected the leads to the Nology coils:
  • Using di-electric grease, one-way spade connectors, and crimping pliers, the leads were permanently attached to the coils.
  • On the PVL sparkplug wires at the coil, the copper end clip circumferences were reduced with pliers. The coil posts were coated with dielectric grease, and the sparkplug wires were snapped into place.

3.) Vacuum hose:
  • The new braided steel vacuum hose was replaced with larger inside diameter nylon braided vacuum hose. This hose is supposedly, "kink-proof," and bought @ BAP-Geon. I cannot remember size at the moment. So far-so good...
  • New snap-clips were attached to both the #3 carb vacuum port, as well as the gas tank.
  • Vacuum caps on other cylinders were dotted with "pookie," and reinstalled. This stuff is a Toyota dealership item. It is not RTV. It is black, and will adhere to anything, including oily surfaces-even curing while fully submerged in oil. I have only had luck removing uncured product from my skin using DEET. If it dries on your skin, it must wear-off. Cured product will ruin clothes, walls...
  • While inserting the vacuum hose clip to the petcock, my hand slipped. Grazing the selector knob, it snapped(Prior to this, the knob was working, and in the correct location, having tested it just minutes before).
4.) Ignition Sensor:
  • As it was originally at 1,0mm gap, per the Triumph mechanic @ the dealership, I re-adjusted it to 0,685mm- being that the shop manual states a gapping range between 0,6mm-0,8mm.
  • Questions: Do any of y'all have the TDC location for Cyl 4 scribed on the metal wheel? Are all igniter wheels adjustable? Mine is slotted, with set screws and 5 setting-lines.
5.) Carburetor:
  • Try as I might, the "witches hats" could not be accessed for inspection. Whoever invented those, and conjured the airbox servicing...Both need to be burned at the stake.
  • I thought long and hard about removing the float bowls again, but looking at the beating my hands took from just the other day, caused me to delay that action.
6.) Gas Cap:
  • I'm not real sure what I was supposed to look for on this one. There were two opposing orange diaphrams with an access channel, I assume connecting them, to outside air. Again, there were two. I removed both. Whether these were the tip-over valves, I do not know. Nothing else resembling valves were noted in the gascap design.
  • Quite by accident during the diaphram extraction, I lost the uber-tiny spring and ball. These I later came to realize function to hold open the metal flap which exposes the key hole in the gasoline cap. Oh well...
7.) Kickstand Kill-Switch:
  • Other than spray some penetrating oil into it's operation, I did not monkey with the switch.

Installing the charged battery and bumping the starter, she immediately started at half-choke. I quickly stopped the choke, and she idled @ approx 1000rpm. I let her idle like this until she drained the carbs, and I buttoned her back-up, at approx 1:30am this morning.

At 5:30am later this morning, I went out and fired her up, again at half choke. Raising the kickstand, I engaged 1st gear, and removed the choke.

Still not 100% confident, I stayed on the freeway access road. Figuring that all that partially emulsified garbage seen on top of the pistons earlier was on it's way out, I piddled-along at a high rpm, while in a low gear.

Gaining confidence, I got onto the freeway and rode into town.

Things noticed:
  • Previous, off-idle hesitation is gone.
  • Much smoother @ idle.
  • Surging has pretty much been eliminated.
  • The occasional hiccup at idle (which typically drops rpm 500-700rpm for 0,5 seconds), has been reduced. I noticed it twice on my 1.5hr commute this morning.
  • Although GREATLY diminished, I still notice this: While steadily holding 5000rpm, there is what sounds like erratic popping, similar to the way an exhaust leak sounds. If there is surging, it is very slight. Also, I cannot locate any areas in my exhaust that appear to be leaking. Any ideas?
Thanks everybody!



Best Regards,

-Scott
 

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You are very thorough. Take what I say with a grain or two of salt since I have Keihins, but I think that you have a Mikuni problem. Known problems are needle seats that fail after about 10 years and main jets and needles that wear out. It also sounds like there could be dirt in a circuit. Balancing your 4 carbs should help smooth out the idle more. How many miles are on your bike?
 

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28k on the bike.
What exactly is required for the swap to Keihins?
This might be a question for the Trophy board. Do late model Trophy 1200s have Keihins?

The Mikunis aren't a lost cause, new jets, needles and float valves and they'll be good for another few thousand miles. The Keihins are just better built in comparison.
 

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Alterna, I would forget about swapping the carbs at the moment. Was the bike running normally before you got fuel a few weeks ago? Or was it acting up but tolerable? If it ran well before you put gas in it I would be suspicious of the fuel. On other forums I've seen accounts of people unwittingly putting Diesel in and having the bikes die as they pulled away from the pump. If you can rule out poor fuel the next thing to look at is ignition. You've done everything but rule out the ignition control box. The bummer is that substitution is the only way to really tell if it is cooked. The factory manual I have shows a tester that connects to it but that is a dealer tool. Does your friend have access to one? Just to be sure you could inspect the harness connector to the igniter for corrosion or poor connections. Writing this made me remember a problem I chased on my racebike,I had a high rpm miss that I couldn't figure out for a couple of weekends.I did everything you have done plus leakdown tests and igniter substitutions. After a killer start and running second for most of the race it pooped on me. Back in the pits everything checked out fine till I just barely touched the ign. switch It turned out that the contacts in the switch were worn enough that vibration at high rpms would cause intermittant voltage loss to the ign. That might be worth a look.
 

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Discussion Starter #12
It was starting to act-up just prior to fuelling. I think I've narrowed it down substantially:

The mixture is getting screwed-up in one or more carbs at 5k rpm. Lower, and higher seem ok. It's more of an annoyance at this point, as performance does not seem to be affected.

While at a light, I went to neutral and grabbed the righthand side carb. Pulling up gently, the rpm raised from 1200-1400. Releasing the carb, the idle immediately went back down.

Just before taking off, I jiggled the righthand side carb. For about a mile, the bike did not pop. Testing the carb boot clamps back at the house, they are all tight(or frozen), not budging at all.

I'll replace the clamps, but I do not think they are culprit. What I think is giving me this annoyance, is the needle valve/seat in the #1 carburetor. Jiggling the carb helping to temporarily seat the needle. That's my best guess without tearing into it.
 

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That does sound like a split manifold boot.Or two or three or four. I think you mentioned previously you had the carbs off. Looks like its time to pull them off again. That would also be the time to fix the needle and seat and double check the jets for contamination. I know its no fun but do it all at once so you won't do it two or three times!
 

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Discussion Starter #15
Update

Giving up, I took the bike to Gulf Coast. 1 carb's jets were almost 100% clogged. A venturi on another carb was damaged, affecting slider movement.

It's nice to know that she'll be right, but I almost needed an adult undergarment when presented with the estimated repair bill.

Anybody need a large upright toolbox, tools included?
 

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The only thing that I can think of is that the o-ring seats for the float needle valves go bad in Mikunis, requiring replacement.
I'm with Sailfish on this one. Had similar issues with mine and a rebuild of the Mikunis was the fix. She runs like it's 1995 again. Got the Mikuni parts from a Suzuki dealer.

Gas degrades\deteriorates much faster these days than it did 15 years ago. Ethanol doesn't help matters either. I always add a little Sta-Bil to each tankful now. Makes a world of difference for keeping the Mikunis clean.

*edit*
Didn't realize you had it sorted.
 
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