Bike over heating after 40 mile ride

[Ken4004]

Had an issue with the bikes engine overheating after going up a step hill so when I stopped at traffic lights the bike died, left it 20 mins and I was able to ride the 20 miles home.
I suspect this is due to either the bikes engine overheating running a bit lean and or timing slightly out.

I did think the bike was running a little rich so because I had run out of adjustment on the air screw I decided to move the carb needle up one notch to lean it out but I think that was too much of an adjustment so will put them back to the middle position.
I have been able to do this without removing the carbs , a little fiddly but possible and means I can complete the task in under two hours for all four carbs which
Isn’t  too bad.

So the plan is adjust needles
Reset air screw to standard position
Recheck points
Reset timing and strobe
And finally sync carbs
Probably would be an idea to check the valve clearance as well while I am at it.

Still running the bike in after engine rebuild so covered 280 miles, I think there is a bit of a flat spot on performance after 5000 revs so hopefully all the work about will improve this, I did consider changing the plugs because I am using NGK DR8ES plugs and the manual says DR8ES-L so not sure what difference that will make.
I did also check the ignition  auto advance assembly for the points to see if that was sticking but it seemed to be OK last time I looked and using the strobe I could see it advancing when the revs increased.

Sorry about all the waffle probably just thinking allowed while typing this, I think another problem is that I am normally riding my Triumph 1050 so I might be confusing the sluggish throttle response with the fact that the performance of the 400 is so much lower so comparing 120 horses with 37 so I really need to ride another bike to make a good comparison.


That’s my day planned out unless the wife has a job for me !

Well you will be glad to here I finished waffling for one day !

[TrickyMicky]

If you raise the needles upwards, that will make the mixture even richer. The needles are tapered, so the higher  position admits more fuel earlier as you open the throttle.

[Mikep328]

A flat spot beyond 5k RPM is essentially the opposite of the way these bikes typically act so clearly something is not as it should be.  I'm curious about the "running out of adjustment' comment re the air screws.  The normal adjustment range is fairly narrow and "running out of adjustment" sounds to me like the low speed circuit is clogged/otherwise not functioning properly.

As far as above 5k RPM, retarded ignition timing could cause poor high speed response.   Retarded ignition will also cause overheating.  A clogged muffler can cause both as well.

I agree that returning everything to the stock settings is the best way to start the troubleshooting process.  Of course that assumes that the various components - ignition system/carbs are all adjusted to spec/working correctly.  So that might require carb disassembly for a thorough cleaning/setup.  Carb float level and fuel flow from the tank should be checked as well as the vent on the tank's cap.  A clogged cap vent can cause a lack of power under high engine load - sometimes it can be bad enough where the engine will idle but not run well in local low-speed traffic. 

FWIW re fuel flow - I once had an issue with an add-on aftermarket fuel filter causing a restriction.  Removing that filter eliminated the problem.  I no longer add any fuel filters; I rely on the ones that came OEM!  Re that - pull the OEM filter from the tank and check its condition/replace if necessary. 

In any case, good luck!!!

[exvalvesetdabbler]

How was the fuel level in the tank?  Was it on the verge of needing to be on reserve? And the strep hill altered how the fuel sits in the tank


Regards
Dave

[Ken4004]

Hi Guys thanks for all the replies let’s answer the questions

I dropped the needle once notch because it was running I thought a bit rich so will move it back to the middle position so stock position

I believed I had run out of air screw adjustment because I adjusted it in small intervals and went out for a ride and I believed it was still running rich.

I had completely stripped the carbs and cleaned everything, fitted new carb kit all except the original needles because they looked good ( what was I thinking school boy error)
I took the carbs apart and fitted the new needles and put the cir clip one notch up to make it run leaner I should have really just fitted the new needles and then tried it.

I have read that regarded ignition can cause overheating but it did look good when I strobed it but will definitely recheck.

I have a pre filter on the tank so this can be removed and see what happens

The fuel cap vent being clogged is a good possibility as I have never checked this .

And finally I did have plenty of fuel in the take when I went up the hill the bike stopped when O was on the level just pulling up to the traffic lights, I also like the sound of the muffler being blocked as it did have quite a lot  of loose rust in it which I thought I had cleaned out which is not easy to do.

Well you have given me a lot to think about but as I said first get it back to stock adjustment then carry on from there cheers guys I keep you updated regards Ken

[K2-K6]

There's a huge difference in torque between those two bikes  and quite different driving style to go with that. The little four really doesn't suit anything towards lugging, but thriving on revs.

Its possibly the most sensitive (of these fours)  in serious consequences, to jetting and especially the effects of running too lean. Certainly good to establish a standard scenario to then evaluate from there I'd agree with.

The plugs, and that L designation. The L should push the plug tip out further into the combustion chamber, that to in effect give a grade of 7 1/2 in NGK terms. This was, in my understanding, to try and mitigate fouling by raising the tip temperature without going to a 7 graded plug. I don't feel that would help here without further analysis, but raise your risk in overheating effects further, which you don't want to do.

If anything, it may help to go to a NGK 9 rated plug to give more safety in margin for plug tip temperature (plug runs cooler) during this evaluation. To ultimately be reviewed when you've established more comprehensively the mixture you've got in practice.

If you're running with E fuel, then the fuel contains, relative to original fuel when jetting etc was specified, more oxygen to impact the decision now being made.

To err on the side of caution in jetting and evaluation is priority for the experience you've just had. It's easy to compromise these engine otherwise.

A question, running out of travel on airscrew, which direction was that, in or out end ?

The flat spot at revs above 5000rpm does tally with lean mixture, the mix being reluctant to fire competently, then opening the throttle with revs not rising (classic flat spot) will drive these slide carbs toward even more lean as vacuum drops and less fuel is pulled from float bowl.

[exvalvesetdabbler]

I had similar issues with the wear in the emulsion tubes giving blackish plugs, confirmed it by swapping in a spare set followed by a new OEM set.  The bike would stumble on  off on the throttle at low revs in traffic , made it a bit of a handful. My son behind me  on the road said it stunk of petrol.

There was corrosion pitting around the top of a couple of tubes.  I could easily see the difference by dropping a needle in and seeing how much it wiggled.

No other changes were made other than swapping out the tubes and needles followed by a static balance.

All caused by leaving the bike for a couple of years with fuel residues in the carbs.

The D8EA was the replacement when the ESL was discontinued.

Regards
Dave

[Ken4004]

There's a huge difference in torque between those two bikes  and quite different driving style to go with that. The little four really doesn't suit anything towards lugging, but thriving on revs.

Its possibly the most sensitive (of these fours)  in serious consequences, to jetting and especially the effects of running too lean. Certainly good to establish a standard scenario to then evaluate from there I'd agree with.

The plugs, and that L designation. The L should push the plug tip out further into the combustion chamber, that to in effect give a grade of 7 1/2 in NGK terms. This was, in my understanding, to try and mitigate fouling by raising the tip temperature without going to a 7 graded plug. I don't feel that would help here without further analysis, but raise your risk in overheating effects further, which you don't want to do.



If anything, it may help to go to a NGK 9 rated plug to give more safety in margin for plug tip temperature (plug runs cooler) during this evaluation. To ultimately be reviewed when you've established more comprehensively the mixture you've got in practice.


With regards to running out of air screw adjustment it was out trying to make the bike leaner, so my theory which I think was incorrect is to adjust the air screw go out for a ride then check the plug colour so kept doing that and still had sooty plugs so decided to change the needle height and put the air screw to 1 1/2 turns out and that’s when I had the over heating issue.
Just to clarity when the bike died it would not even turn over until it had cooled down , never tried to kick start because it was so hot.
Let it cool down for about half an hour and it started with no hesitation.

Carbs now back to stock needle position and air screw at 1 1/2 turns out from fully in , going to see what it runs like and recheck the timing / advance etc.

If you're running with E fuel, then the fuel contains, relative to original fuel when jetting etc was specified, more oxygen to impact the decision now being made.

To err on the side of caution in jetting and evaluation is priority for the experience you've just had. It's easy to compromise these engine otherwise.

A question, running out of travel on airscrew, which direction was that, in or out end ?

The flat spot at revs above 5000rpm does tally with lean mixture, the mix being reluctant to fire competently, then opening the throttle with revs not rising (classic flat spot) will drive these slide carbs toward even more lean as vacuum drops and less fuel is pulled from float bowl.

[Mikep328]

From the experience with my 400F over the past few years, the bike will run great on  E10 fuel with totally stock settings on everything - jet size, needle position, airscrew turns, STOCK type muffler and stock air filter/airbox.   As noted, leaving untreated fuel (without some sort of fuel storage additive) in the tank and especially in the carbs for extended period will have bad results. 

[exvalvesetdabbler]

Since splashing out on OEM brass ware 15 years ago I take no chances now. I used an ethanol protection additive at each fill up. I keep a 8 ml bottle of it in my jacket  pocket.  Then at the end of the season I flush the carbs through with white spirit and then refill them with white spirit with a dash of oil in it.

Even with  these precautions the brass ware still goes dull. Yet brass ware out of old carbs that's not seen unleaded fuel still looks like brass and the float bowls look like new inside.

Mine got into such a mess before the when it had been parked for 3 years when I worked at sea. Carbs had been emptied but not flushed out.

Regards
Dave

[Ken4004]

Here is a picture of one of the spark plugs I took after I got home from my ride when it over heated, it looks normal to me but you might not agree .
Light tan colour which according to the manual is the normal colour , all spark plugs look the same.

[Ken4004]

I did have a look at the breather hole in the fuel cap but couldn’t see a way of taking it apart easily.
Rain stopped play this afternoon but managed to get the carbs back to standard settings , c it checked the valve clearances which all look good, reset the points gap so will if I get time tomorrow recheck the timing snd rebalance the carbs.
If I get time I’ll take off the silencer and give it a tap with a rubber mallet and see if any more rust comes out.
I don’t think you can remove the baffles out of this Silencer as it appears to be welded together unless anyone knows different.

[exvalvesetdabbler]

Here is a picture of one of the spark plugs I took after I got home from my ride when it over heated, it looks normal to me but you might not agree .
Light tan colour which according to the manual is the normal colour , all spark plugs look the same.

I would call that black/sottey

[Skoti]

I had similar issues with the wear in the emulsion tubes giving blackish plugs, confirmed it by swapping in a spare set followed by a new OEM set.  The bike would stumble on  off on the throttle at low revs in traffic , made it a bit of a handful. My son behind me  on the road said it stunk of petrol.

There was corrosion pitting around the top of a couple of tubes.  I could easily see the difference by dropping a needle in and seeing how much it wiggled.

No other changes were made other than swapping out the tubes and needles followed by a static balance.

All caused by leaving the bike for a couple of years with fuel residues in the carbs.

The D8EA was the replacement when the ESL was discontinued.

Regards
Dave

Been there and seen that, good post and good advice.

Absolutely agree...

[exvalvesetdabbler]

I don't think fuel flow is the issue here, you're getting more than enough.

Time to check the easy bits before tearing stuff apart too much
 
Spare bit of pipe on the fuel tap into a clean recepticals and try the fuel tap in both pisitions

Choke flaps fully open once the leaver is clicked in the open position
Corrosion inside the post where the main jet sits, or fuel getting by the o ring
Float heights  are the float valves sealing or allowing the fuel level to rise too much

Clean plugs with a blow torch before trying again. There's always a risk that you have cleared the problem but not burned the crud off the plugs during normal running.

Sounds like you are going through the same mill I did 15 years ago.  I replaced all the brass ware in the rebuild kit but the needles and emulsion tubes are not in the kit.


Regards
Dave