Starts, runs great. Warms up and dies intermittently.
 

Ok, I am giving in and asking for help.
My VTR starts, idles and runs great. Goes like crazy, but sometime (2-10 miles) into the ride it will cough once as if to warn me, then dies completely about a second later. The way it dies almost seems like electrical, since it does not provide warning the way running out of fuel normally would. Sometimes it dies during hard accelleration, sometimes during steady riding, once it died at a stop light while idiling. The engine will normally start right back up (sometimes 5-10 min wait is needed) and allow me to continue, but will then die again sooner than when cold, it seems.

"Barn find" Superhawk sat for 5 years.
I purchased it and did the following:
Plugs, CBR coils, RR. MCCTs, tires. I only have about 70 miles on it now.

Air fuel mixing:
Carb cleaning and "Hawk mods".
Stock air filter and all original CA smog items are intact and connected.
New vacuum hoses . Slide Diaphrams are in good shape and seated ok. Did synch the carbs. Have not adjusted mixture screws (idle drop) yet.
Tank Feed
Because of all that I have read, I removed the petcock and disassembled it. Its diaphram is also good. I cycled it on and off with a test vacuum and it dependably opens and closes the flow of fuel every time. Yes I have it connected at the inlet port (BTW, there seems to be a built in check valve at this port) at the back of the petcock not the vent that points down. I ordered a new diaphram repair kit to be on the safe side.

Switches:
I have not test jumper any switches, but did cycle the kickstand up and down a hundred times and wiggled the ignition switch and kill switch and do not find these to be a problem so far. The engine stopping does not seem to be associated with any bump in the road.

Can anyone give me some other ideas? What areas would you go after ?
Besides simplifying, is there a benefit to removing the emissions controls? I don't mind keeping that stuff on there. but if I supect it to be causing a problem, don't mind removing it either. For example, the tank vent seems to be venting ok, but it connects to that cannister. I am not sure what is going on with that can during running. Maybe I should try a temporary vent tube to atmosphere now that I think of it. Will try that tonight.

I am returning to Moto ownership after a 25 year period with little riding done. As you can imagine, this is not a good, confidence inspiring way to get back in. I need to concentrate on my riding skills, not my pushing bike along the road skills.:o

Does this only happen, perhaps, when your gas tank is very full?

It sounds like a carb fart, but you did sync the carbs, which should keep that from happening. What method did you use to sync the carbs?

Thanks for asking. I have not noticed a difference in the tank level since I have not had a chance to put that many miles on yet.
When this happened (currently), I would say it has about a half tank.

Probably not a vaporlock issue caused by an overfilled tank then.

I did synch the carbs and checked them again after pulling the carbs last.
But the engine once died while motoring along a at 55mph. VVrrrrrr, nothing , no power, no bucking, quickly pull in clutch and look for space along the road to coast to.
I use a u-tube filled with transmision fluid . It's pretty sensitive.

So it cuts off with no boom, thump, backfire, or fanfare? Just silence, and will always re-start?


Mine has the intermittent "clunk-die" while idling at a light, but I'm pretty sure that is a fuel delivery issue - i.e. combination of mixture/carb synch/low idle.


That said - you only need two things to run - spark and fuel.


How do the sparkplugs look? Does it immediately re-start, i.e. cruising along, dies, pull in the clutch hit the button and it runs again? That to me would be carburetion/fuel issues. Maybe junk in the float bowl clogging a jet at an inopportune moment.


I would think an electrical issue - wire rubbing on the frame and grounding out, sidestand switch or kill switch shorting out - would not always immediately re-start - sometimes the short would remain shorted, others it would just momentarily touch the frame causing the issue.


Unplug the sidestand switch, you can short out the clutch sensor switch, and I even think it will run with the kill switch unplugged - but it's not really safe to ride that way in the event you need to kill it quickly.


You might take a flyer and re-clean the carbs, and inspect inside the tank with a flashlight to look for more junk. My carbs took two sessions to get really clean.


Good luck - trial, error, and observation is what it takes. Trust me, I've been to the edge of the "screw it I'll just buy a new R1" ledge a couple times!

Thanks for the input Andy.
The plugs are new. It does restart after a minute or so. But the problem does not correct itself on the fly. In other words, no bucking and then running fine again.
I will try to defeat the switches next, and install tubes to the float bowls (for draining/judging if fuel is there) to see what that tells me.

Have you tried opening the filler cap when it happens?

If you hear air getting sucked into the tank when you open it or the bike fires up again right away, then you have a tank vent issue, which this does sound like.

Oh and you need 3 things to run, unless you can get it to fire with no compression ;)

Ha, yes! Compression too.
Thanks for the venting idea. I will put a spare key in the cap next ride.
But by the time I coast to a stop, get my helmet and earplugs off, it may be equilizing.
That brings me to this question. If the fuel feed was locked up, would that shut the engine down so quickly? Even if the petcock was shut suddenly, would it feel like someone his the killl switch? I have been wondering this.

When you get a vacuum lock it just dies.

Then will take a few minutes before it will start again if you don't open the cap.

OK, then this is one item I will be focused on tonight.
If you see a tired guy pushing a bike, at least wave.

I did not have a lot of time to work on the problem last night. But did run a vent hose to atmosphere and took off for a ride.
All was good for about 10 miles and I was feeling good. Then while idling for a couple minutes at a light, tried to launch and it happened again. This is the second time the problem occurred after idling for a while at a light after a long run. This time there was some stumbling and it did stay running, just not enough power to move so I scooted it out of the intersection with my feet.
So I opened the fuel tank cap, restarted and continued with the cap ajar. No problem all the way home.
But this is not conclusive since the problem comes and goes. It always runs and idles great! Until it doesn't. Will update later.
Any more ideas out there? The tank vent seemed to be clear last time I had the tank off.

sounds like a dead coil to me when it gets hot, can you tell which cylinder is firing bad? and trouble shoot from there im no expert so take what i said with a grain of salt but was it bad before you changed to cbr coils? if u still have the old ones and their not dead you can use them to test with just my 2 cents. and good luck with it mate

This thought crossed my mind. The old ones were fine but are gone. I'm going to get another set of coils to test your theory. Thanks.

Still sounds like a vacuum lock issue.

I would make sure the vent line (the metal bit on the tank) is clear with high pressure air and a bit of wire just in case a bit of crud has worked its way into the tank itself.

Thank you for that. I should have thought of this from the beginning since that tank has been off the bike for 5 years! An invitation to gas loving spiders and other web spinning creatures.
I looked at my standard Honda manual which does not seem to show the Tank vent detail. Perhaps an inverted trap or maybe has a little bobble cap on the end?
A new petcock diaphram kit showed up also so I will be pulling the tank again tonight.
Amazon.com: K&L Supply Fuel Petcock Repair Kit 18-5015: Automotive

Edit: The parts I received from the link above had a differently shaped "stopper" and would not shut off the flow.

definitely work to clear the vent line into the tank. With the cap off you should be able to blow through the line to your hearts content.


I had a dirtbike with a clogged tank vent once - same thing - would run just fine - until it wouldn't. Pull off the track, open the cap, whoosh, bike would start right away.

I removed the tank and checked the vent line which was clear.
Tried to install the petcock kit I mentioned above. The smaller rubber parts that is the "stopper" was shaped differently so had to put the old one back in!! Things were not going well. I nearly started tearing into the carbs again with the intent of checking for debris and deleting the extra smog stuff. But I looked at all my nice work with all the new tubing and thought " I'll put it back together and test one more time".
Well same thing at first , drive about 4 miles and then it cuts out. I pull to the side of the road (just like before) put it in nuetral to restart (just like before) Engine starts right up (just like before) .
But then something different happened. I dropped it into first and it dies. Hmm, I left the kickstand down? Nope. Ahaaaaa! I restart and drop into first. Dies again! This never happened before.
So I realize that the kickstand switch is likely the problem after all. When cool, it works fine. But when the exhaust heats up the switch, it starts opening for some reason. When I pull over and put it in nuetral, it starts (every time of course) and must have cooled enough to close again so I could be on my way. This time, the switch must have deteriorated to the point where it gave itself away.
I jumpered the switch out for now and since have yet to have a problem.
New switch is on the way. Thanks for the help as always.

That exact same thing happened to me with the sidestand/kickstand switch. Switch was bad.

Attachment 22051

These switches are nicely engineered.
I knocked this one apart to see what I could see. It was clean inside, but one of the spring ends where it makes contact was worn or had been arcing.
Replacement on the way.

Yay u found it

Good work on solving your problem, and thank you so much for posting up the details. As a relatively new SH owner I like to know about these things before they happen to me.

I had learnt about the vapour lock issue with the tank during my "pre-purchase net investigations", and was glad that I'd paid attention, because it happened to me the very first time that I re-fueled the bike. Just prior to this I had been doing all sorts of work (oil and and air filter changes, MCCT installation) so my first thought was 'dang, I've screwed something up'. The vapour lock causes the carbs to run out of gas, so if you've owned an older bike with a reserve fuel tap, the symptoms are pretty obvious and familiar, but not sudden as you described.

I had some issues with the fuel tap on my bike (probably due to being disturbed after a long slumber) that resulted in an overflow through the carbs when parked. You are correct that the vacuum diaphragm does have a check valve built into the port, as I understand it this is to keep the fuel tap open for a short period when the vacuum signal is lost or low. However the check valve should also slowly release over a few seconds so that the fuel tap shuts fully when the engine is off, and mine was not doing that, an age related problem I suspect. I was able to poke a small screwdriver into the hole on the inside of the vacuum fitting and magically freed up whatever was blocked/jammed, and the petcock started working as intended.

I purchased a Honda part 16953-MLO-034 which contains the exact OEM parts of the diaphragm with its two outer shells.