Problems with Long Highway Hauls?

[allanrps]

So I took my XS on a first attempted road trip earlier this week, and I now have a couple concerns with the bikes ability to handle touring. Before I left I had the bike in what I judged to be top condition. Started first kick when I judged the temp right, idled steadily, pulled evenly, sparks read perfect, and got good mileage. On the trip, however, I encountered some problems.

After riding one tank almost dry , my bike stalled coming to an intersection off a highway exit. The bike just didn't want to idle. I would kick it, rev it a little, but it would fall right through. I figured it was just hotter than I had ever gotten it in town, so I just adjusted the throttle stop screw and got it running. Figured problem was solved. I still had the problem later, although only occasionally.

Another thing was that occasionally the bike would really buck when pulling from a stop. Never had this problem in town, only after long highway runs. It would stumble and sound like it was misfiring, then I'd get a couple of strong hits. After it got rolling, it would not misfire or stumble at all. I only remember having this problem after taking the bike on a gnarly offrode trail and dropping it a couple times, but I don't perceive how that could cause it.

Finally, I occasionally have a problem where the bike will misfire at idle. Usually it will just stumble and then catch again, but sometimes it will just stall. I had this happen once or twice like a week before the trip, but I just wrote it off, as the bike had been running flawlessly for some time. The problem definitely got way worse during the trip. After long highway runs, I would lean on the idle a little bit because I was scarred the thing would stall. Even with the littlest bit of throttle, this problem is non-existent.

It's worth noting that I discovered a gasket leak in the right cylinder which only showed itself after the first 100 miles of highway. Had oil splattering my right carb and peripheral instruments. It wasn't much though, so I just monitored my oil level and topped off when necessary. Spark plug was clean, so I didn't worry. I also suspect that my routing of the crankcase vent to my K&N air filter might be spitting oil into the carbs. It's pointing the opposite direction, but I did notice some oil buildup in the air filter last time I took it off. I figured that was basically the stock setup anyway, so it shouldn't be a problem, but now I'm forced to consider it.

Does anybody else have problems with their bike after long runs on the highway? Or could my problems be caused by one of the things I listed?

Thanks,
Allan

 

[16VGTIDave]

Check for vacuum leaks and correct if found. Check/adjust valves. Adjust idle mixture and sync carbs after riding bike on highway for 20 min or more. Sounds like the idle mixture may be off. Do you have an inline fuel filter? If not, check/clean carbs and install filter. Check ignition timing. Inspect ignition coils for overheating - leaking.

There will always be some oil vapours coming from the crankcase vent and it isn't a problem unless it begins causing smoke. Full synthetic oil will reduce this. My bike burns less oil on the highway than in the city. Virtually none on the highway.

I have successfully ridden 400+ km (250 mi) without stopping and without issue. The only time I've had issues on the highway was when I was running WOT for more than 30 seconds at a time. The vacuum petcock (from FJ600) was not delivering enough fuel. Switching to Prime while riding fixed that annoyance.

 

[allanrps]

I checked previously and found no leaks. Boots are new and everything is tight. Carbs were synced and idle optimized when the bike was warm, but not after a highway run. I've got a fuel filter and I cleaned the carbs and put them together spotless a couple months ago. I'm not sure about the valves, I'll check those when I replaced the engine gasket. Setting the timing will be tricky because I have a non-stock flywheel. I made markings for the current fire timing, but I don't know how I would accurately adjust it without using trial and error, which would be grossly impractical since the problems only show after long, tough rides. Thanks for the tips

 

[XS400NJ]

My 3 usual suspects would be:
1. spark plugs - easiest to try: just replace them with new ones and if no difference - replace back and keep new ones for future. Check old plugs for little carbon hills growing on electrodes.
2. dirt in carbs - long rides involve a lot of bumping and jumping, which can lift dirt from bottom of carbs and clog passages. Unfortunately this one is tough to diagnose and all you can do is to take carbs apart, clean, and install inline filter.
3. ignition timing - if you have points, check that nothing is stuck between them, check the gap(it goes smaller as slider is used-up ), and check advancement mechanism - weights must return back with confidence and should stay in place until engine reach about 2500rpm.

there are of course other things to check, low valve clearance could cause problems on hot bike(after long run).

just my 2 cents...

p.s. do not go "trail and error" route in setting timing, just find TDC by observing the piston move and set timing to as many degrees back as manual said.

 

[allanrps]

Thanks for the tips! I will set the timing how you described.

I think I actually have an engine problem now... I hear a tin pinging/rattling sound coming from the right cylindar. I will post a video of it, but it doesn't really capture the sound that well. That is the cylindar that has the leak. After I got home from driving like 300 miles, I found that my oil was reading below the mark on the dipstick. I refilled it and started it and only then noticed the noise. I was probably just too tired to notice it earlier. I guess I'll check it out when I replace the gasket... Any ideas what it might be?

 

[allanrps]

From what I've read it seems like it's most likely to be a valve clearance issue. Hopefully that will solve all my problems.

 

[xschris]

Sounds like the rockers/valves are loose or out of adjustment. Make sure the the bike is full of the proper weight oil also.