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New problem: overheating, stall on downshifting and lower idle

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New problem: overheating, stall on downshifting and lower idle

Old 08-21-2011, 09:22 PM
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New problem: overheating, stall on downshifting and lower idle

Hi guys,

If it isn't one thing it is another...

I just went on the official test drive to determine that my oil pan leak problem was fixed good enough to commute to work on my SH.

I gassed it up and went for a little ride with a few cruising speed highway passes (~130 kph). When I exited from the highway and was down-shifting for a 90 degree corner I think when I was shifting from fifth to fourth the engine just stalled and the back wheel locked up for a split second scaring me $hitless. Clutch in and it started up fine and I carried on albeit slower. It stalled a few more times on the way home, all while I was on the move. I smelt some slight burning smell but I thought that was part of the smells of the construction zone that I was in. About 1 km from home I notice the temps were just below the red zone and that the bike was idling below 1000 rpm at red lights. Prior to fixing the oil leak the bike idled fine around 1200 - 1300 rpm.

When I pulled into the driveway the bike stalled again and I saw a big puff of steam pour out of the front end just as it was stalling... I think this was a pressure releif valve of the cooling system, but I haven't got into yet. With the bike in the garage I verified that the coolant reservoir was still half-full, just how it was when I added to it last week. Oh, and just as it was stalling, the radiator fan kicked on high speed. I'm not sure if the fan was on while I was riding/stalling.

I've seen a few threads in here which describe the process to verify water pump and water temp switch. So obviously I'm going to have to do all that. The only real symptom that I recall is that after fixing the oil pan leak, when I fired it up I saw one drop of coolant on the ground which looks like it came out of the right side radiator.

So I've got a few questions:
Does it make sense that the bike stalled when it overheats?
What would be the order of things to check to tackle this problem?

Any help is much appreciated. I'm at the point where I might just bring it into a local shop near my work.

Thanks,
Jim
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Old 08-22-2011, 01:10 AM
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Start with the simple stuff first. Is the cooling fan on the right radiator spinning freely? If yes, check the temp switch. If you can't get the fan motor to spin, check the appropriate fuse.

If the fan system works, drain, flush, re-fill cooling system.
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Old 08-22-2011, 06:59 AM
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It sounds like his fan kicked on, so that may not be the issue....

+1 on flushing the coolant... air in the system can cause a lot of problems. You can drain the coolant by taking off the water pump cover (3-4 bolts, can't remember fully). When you do this, it's easy to make sure the water pump is working. Try to spin it by hand... if it spins, it's broken (the teeth are engaged to your motor, so are locked). Then turn the bike on... the pump should spin (making sure nothing is touching it, of course). If all that checks out, your pump is working as it should.

When filling with coolant, try hitting all of the hoses with the back end of a screwdriver after it warms up slightly. This works any air bubbles out that may be stuck in them. I squeeze them too, and blip the throttle, to try to work them through the system. Not sure how all of this relates to your stalling, but it seems like a good place to start.
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Old 08-22-2011, 07:20 AM
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I had a similar overheating problem on my bike. I did a flush, checked the thermostat and water pump to verify that they work. After I got those done I started checking hoses for a clog, it ended up I had one in the hose that runs from the overflow tank to the right radiator. (It's the smallest line, so it would be the first to get clogged.) If a thermostat and water pump check don't turn anything up I'd recommend you inspect all your hoses and your overflow tank.
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Old 08-22-2011, 07:24 AM
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Thanks for the replies so far.

For sure I'll start with the easy stuff first. The coolant drain/flush/refill doesn't sound too difficult. Hopefully I can get that done today.
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Old 08-23-2011, 12:48 PM
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I drained the fluid and it looks like it was about half a litre down of the almost three litres that the system should hold.

I pulled the water pump cover and the pump wheel did not free-wheel at all with engine off. With engine on, the pump turns fine.

I buttoned it all back up and went on another test ride and still the bike would sometimes die when down shifting... not always, but maybe once every 6-7 times that I need to down-shift. On my 15 km test ride the temperature did get above the midle of the gauge, but the fan had turned on and was almost cooking my right leg.

On a slightly similar note, but maybe somewhat related, my homebrew alternator cover gasket doesn't seem to be doing its job fully. My left boot after the test ride was covered in a few drops of oil, and when I parked my bike I promptly found a fresh drop of oil on the ground beneath the alternator cover.

Since my idle speed is a little lower than 1200 rpm, could the bike just be stalling if I'm not being careful when I blip the throttle on down shift... I tend to blip the throttle twice on down-shift at that is what they taught at the Motorcycle Safety Course. I think it could be shifting in between blips.

I my next guess is to adjust idel to exactly 1200 rpm when its warmed up and go on another test ride.

I'll try the above for sure but am open for suggestions.

Thanks,
Jim
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Old 08-23-2011, 07:20 PM
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Problems solved!!!

Well, I'm quite happy right now because the bike is now running like a top.

It turns out what I thought was a terrible homebrew alternator cover gasket ended up being a loose alternator timing cover bolt. There were only a few thread holding the bolt on. Well that was easy!

At the same time I adjusted my idle to 1500 just to check that increasing the idle would solve my stall on down-shift problem.... and what do you know, it didn't stall on a 30 km test ride.

The main reason for the longer test ride was to verify that I was going to overheat again. My previous evening's test ride didn't fully satisfy me that everything was ok. Only once did the temps get up to one line past half on the temp gauge. The fans was blowing hard and cooked my leg.

Well I'm happy to say that everything is now working as it did, with the except now all the oil leaks are fixed, and my ride should be more reliable WRT to manual cam chain tensioner. Sweet!
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Old 08-23-2011, 07:21 PM
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Oh, and I reduced the idle a little so now its about 1350 rpm and eveything is still working fine. I'll keep reducing it in little incremenets until my idle is as low as it can go without having the stalling issues.
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Old 08-23-2011, 07:46 PM
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One other thing you may check is that your pilot screws are adjusted correctly... you may be running a little lean, which could be causing the idle problems...
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Old 08-24-2011, 12:30 AM
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Originally Posted by 7moore7 View Post
One other thing you may check is that your pilot screws are adjusted correctly... you may be running a little lean, which could be causing the idle problems...
Not to mention, synchronising those carbs... I can set my idle to 1000 and it still won't stall...
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Old 08-24-2011, 06:20 AM
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Yep- I've synch'd the carbs without setting the pilot screws after cleaning them, and the bike sneezed itself to death, so doing both is probably best
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