Hesitation / vibration at full throttle - Wrist Twisters
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post #1 of 25 Old 10-18-2017, 07:46 PM Thread Starter
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Hesitation / vibration at full throttle

I have a minor problem that is bothering me. I have owned my 2002 919 for a little over a month. It has just rolled over to 39,000 miles. Most of the history of the bike is unknown to me. The guy I bought it from owned it for 2 years but very few miles. He replaced the FPR, fuel pump, and at least 1 injector. Onto the problem:

The bike has a very rough cold start. It's idles fine but when I'm leaving my driveway if feels more like it's running on 3 cylinders, or it's choked. When the bike warms up it has a vibration that can be felt in the engine at 3-4K RPM under more than 1/2 throttle. Full throttle makes it very noticeable. I have replaced a K&N air filter with an OEM. I have replaced the plugs with the OEM NGK. I found a vacuum line that was not installed on the throttle body. When I reinstalled the vacuum line the FI light flashed a code indicating the TPS had a fault. I removed the vampire clip and soldered the wire, someone had previously removed a power commander it appears. All the things I've done to the bike have incrementally improved the running, but the cold start issue and stumble at WOT are still there.

I plan to do a valve check / adjustment this winter. Any ideas in the mean time? Tomorrow I'll probably pull the gas tank, trace the vacuum lines, as well as pulling the pump assembly out and giving it a visual. I also intend to check the FPR vacuum lines for gas.

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post #2 of 25 Old 10-19-2017, 08:30 AM
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I would double check all of the wiring going to the coils. The small control wires seem a bit fragile and could be broken. I would also check to make sure the plug wires are going to the right cylinders.

Good luck!

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post #3 of 25 Old 10-19-2017, 10:28 AM
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Maybe when you first fire the bike up try quickly feeling the header pipes and make sure all 4 are heating up evenly. Easy way to see if any/which cylinders are playing up. Seems strange previous owner may have replaced an injector or two. I'd be looking into this as well. Maybe swap injectors around and see if problem carries over.

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post #4 of 25 Old 10-19-2017, 12:09 PM Thread Starter
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I am actually leaning towards a coil problem now. I checked all of the vacuum lines just now and went for a test drive. Still the same rough running cold engine. Brought it right back home and header pipes 1 and 4 were substantially cooler.

When asked about the replacement of the fuel components, the previous owner told me that the bike was being sluggish.

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post #5 of 25 Old 10-19-2017, 12:21 PM
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If your coil connections are OK try swapping coils and see if problem carries over. The coil for 1 and 4 could be on its way out.

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post #6 of 25 Old 10-19-2017, 01:35 PM Thread Starter
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Well back to where I started. Swapped the coil around and I now see that itís just cylinder 1 thats running cold, couldíve been the whole time. The problem didnít move with the coil for sure. Gonna see if I can swap a couple spark plug wires around now.

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post #7 of 25 Old 10-19-2017, 02:17 PM Thread Starter
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I swapped the #1 and #3 plug wires and it did not seem to make a difference. Iím going to pull the plugs now and look them over. I guess it could be an injector problem. Who knows?

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post #8 of 25 Old 10-19-2017, 02:50 PM
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Pull all 4 spark plugs and check the plug gap. I know you said you replaced them, but did you inspect them for proper gap before installing? I have also seen "new" plus dropped while still in the box and this can break the ceramic insulator or bend the electrode. Also check the plug color to ensure they are all running correctly. Could have a severely rich or lean condition on one or more cylinders.

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post #9 of 25 Old 10-19-2017, 02:52 PM
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Is the number one plug wet with fuel? Could be an injector problem. Especially since you mentioned PO possibly replacing one. That's a little weird. Never really heard of an injector going bad but I suppose it does happen. You could try swapping injectors. See if problem moves. My bike had sat for many years, empty of fuel. Condensation, rust and such had formed. I pressume because the bike sat leaned over much of the crap had settled at the end of the fuel rail and collected in the basket strainer on the intake side of the injector. Partially blocking the injector intake. I took all injectors off. I used a syringe, jammed an injector in the fat end, pressurized syringe with brake cleaner and activated injector with 12v battery. Cleaned em out good.

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post #10 of 25 Old 10-19-2017, 02:56 PM Thread Starter
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I replaced the plugs with OEM NGK CR8EH-9 less than 200 miles ago. I just pulled plugs #1 and #4 because they are easy to get to. The problematic cylinder #1 plug is fouled. Cylinder #4 looks perfect. I checked the resistance across the injectors as well as the current at the plugs and all is normal. I suppose pulling the fuel rail will be my next step.

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post #11 of 25 Old 10-19-2017, 03:05 PM
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If it's fouled doesn't that mean it's getting fuel and it's not being burnt. Which would mean that it's getting fuel (injector working) and has no/weak spark? Or its getting way too much fuel and it's fouled from being over rich? A headscratcher for sure. I'll think on it. Can injectors get stuck open?

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post #12 of 25 Old 10-19-2017, 04:53 PM
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Did a Google search. Turns out injectors can get stuck both closed and open. Try swapping injectors after looking for obvious problems like crap where it shouldn't be. See if the problem moves. Read your initial post again looks like PO had some fueling problems. Did he replace the in tank fuel filter? And what was wrong with the injector/s he replaced?
Could number 1 cylinder bore or piston rings be damaged and the plug fouling from engine oil?
Timing issues?
For what it's worth Partzilla has a sale on honda 919 OEM parts at the moment. Injectors are about $114 I think.

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post #13 of 25 Old 10-19-2017, 05:28 PM Thread Starter
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Hesitation / vibration at full throttle

Okay I did some more digging. Much more. The intake boot on the #4 cylinder is in horrible shape. Iím sure it was causing a vacuum leak. Took the fuel rail off. Their was a bit of rust underneath the problematic injector. I have 3 other used injectors. I moved the injector in question. To see if the problem moves. Going to be apart for a few days until at least two intake boots can get here. Also going to order pair block off plates and a fuel filter.

I donít think their is any engine damage but have no way of being sure at the moment. A valve adjustment will be done soon as well.

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post #14 of 25 Old 10-19-2017, 05:50 PM
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Well done. I reckon your on to it. I almost suggested check your intake boots for leakage, honest. Ha ha. That fixed should sort a bit more out. Vacuum leaks there would cause all sorts of fueling issues. Cut open the old filter and get a bit of an idea of what's been in your fuel system. Post an update when it's back together.

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post #15 of 25 Old 10-19-2017, 06:31 PM Thread Starter
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Hesitation / vibration at full throttle

Will do. I appreciate all the suggestions. Iíve had Hondas on and off for years but Iím new to the 9er. Looks like there is a small bit of rust in the tank. Nothing loose. Iíd hate to coat it, but will if I have to.

On a side note, the stamp on the engine is not the VIN on the frame so Iím assuming the engine is not original.

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post #16 of 25 Old 10-19-2017, 09:06 PM
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If you decide to coat the tank I recommend RedKote

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post #17 of 25 Old 10-19-2017, 10:29 PM
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My original tank had a lot of rust inside. I brought a brand new tank from partzilla, on sale, last year same time as now. They seem to have a sale on honda 919 at this time of year? I will get some small stuff from them while on sale. I checked out tank prices and you can get a brand new tank for just over $500.

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post #18 of 25 Old 10-21-2017, 10:19 AM
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Quote:
Originally Posted by Coondawg07 View Post
Okay I did some more digging. Much more. The intake boot on the #4 cylinder is in horrible shape. Iím sure it was causing a vacuum leak. Took the fuel rail off. Their was a bit of rust underneath the problematic injector. I have 3 other used injectors. I moved the injector in question. To see if the problem moves. Going to be apart for a few days until at least two intake boots can get here. Also going to order pair block off plates and a fuel filter.

I donít think their is any engine damage but have no way of being sure at the moment. A valve adjustment will be done soon as well.
If one boot is duff, I'd be suspicious about the other 3 as well.
Past that, I was wondering if one of the injectors was not properly reseating fully closed after opening.
Only a weenie itty bitty piece would be needed to do that, and such small fines can get past the in-tank filter.
Good on you for figuring it all out.

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post #19 of 25 Old 11-12-2017, 07:22 PM Thread Starter
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Hesitation / vibration at full throttle

The bike isnít complete but I have an update. While I had it this far apart I decided to do a valve adjustment. Had about 6 valves out of spec. What surprised me is that the bike was retarded one tooth out of time. It took me some trial and error but I got the valves adjusted and the bike properly timed. All my parts came in except.... you guessed it, half of my intake boots. I ordered four and only received two. Iím taking the back order time to do some powder coating as well as replacing a damaged swing arm, leaky stator cover gasket, chain and sprockets, and fork seals. I was going to coat the gas tank, but after ordering some red kote I came across some bad reviews. I now believe Iíll just replace the fuel filter, clean out the minimal rust, treat the tank with some 2-stroke gas, and hope it doesnít spread too much next year. Thatís my long winded updated.

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post #20 of 25 Old 11-13-2017, 10:55 AM
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Quote:
Originally Posted by Coondawg07 View Post
The bike isnít complete but I have an update. While I had it this far apart I decided to do a valve adjustment. Had about 6 valves out of spec. What surprised me is that the bike was retarded one tooth out of time. It took me some trial and error but I got the valves adjusted and the bike properly timed. All my parts came in except.... you guessed it, half of my intake boots. I ordered four and only received two. Iím taking the back order time to do some powder coating as well as replacing a damaged swing arm, leaky stator cover gasket, chain and sprockets, and fork seals. I was going to coat the gas tank, but after ordering some red kote I came across some bad reviews. I now believe Iíll just replace the fuel filter, clean out the minimal rust, treat the tank with some 2-stroke gas, and hope it doesnít spread too much next year. Thatís my long winded updated.
Someone else was in there before you were.
And to fit it back together with one cam out by a tooth, might also mean his/her clearance checks were of the same quality, so see "6" with a grain of salt.

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post #21 of 25 Old 11-13-2017, 12:54 PM
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With all the loose fittings, timing out, valves etc it looks as if someone has at least had the head cover off. You did mention that perhaps the bike has had a engine swap. Glad to hear you are sorting it all out. More than one thing off. Also a damaged swingarm. Your bike has had some abuse.
I had a rusty tank. Cleaned all the rust out using a toilet cleaner. Ate all the rust. Took about 4 hrs.
Keep us posted.

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post #22 of 25 Old 11-16-2017, 03:28 PM Thread Starter
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I actually had the cams out several times. It is all timed and clearanced correctly. I still have a rough running problem. Next time Iím off (Monday) Iíll replace my fuel filter and trace down any other gremlins I can find. If the fuel filter donít help, Iím gonna look at sending off the injectors for cleaning or the possibility of a damaged coil wire which I cannot see any evidence of. While I had the bike apart I replaced the plug wires with a set off a 900rr so thatís out as well. Iíll try swapping the coils as well.

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post #23 of 25 Old 11-16-2017, 04:56 PM Thread Starter
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Also went out and swapped over to the 900rr coils just to be sure. No noticeable difference. May pick up a used set of injectors to rule that out as well.

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post #24 of 25 Old 11-16-2017, 05:51 PM
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I think getting a new fuel filter and injectors cleaned/replaced would be a good move. Perhaps give the fuel pump a good look over and it's intake screen. When you replace your filter cut your old one open and have a look.

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post #25 of 25 Old 12-12-2017, 10:04 PM Thread Starter
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I finally have success. I replaced the throttle body / injectors as a unit with a part directly from eBay. The bike runs 100% now. Just like a new machine. The difference is night and day. The problem was clogged injectors Iím sure. I also got the rust out of the tank and replaced the fuel filter while it was apart. Thanks for the help and encouragement through it all. Now Iíve got cosmetics to worry about.
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