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XL500S dies when I down shift and slow down

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So I bought this 1980 Honda XL500s. I've adjusted the valves, tightened the cam chain, adjusted balancer chain, changed sparkplug. It runs well but has some issues

 

A couple issues I have:

1) The rocker arm shaft seals are bad, and there is a minor low pressure oil leak coming from the shaft. It can drip down and get around the spark plug. I just sprayed some permatex leak repair on it to see if it holds the oil back. 

I'd rather not change the shaft O-Ring because that means I'd have to take the head cover off which means I'd have to lower the engine into the frame. Ugh. Also, the rocker shafts are held in by dowel pins which I hear are a pain in the ass to remove.

 

2.) here's the bigger issue I have that I'm hoping someone can help me with. If I ride the bike more than 5 miles or so, the engine sometimes dies when I'm slowing down. For example, I'm riding at a high RPM and I slow down quickly by down shifting. If I let the bike idle just at that moment, it dies- and then its really hard to start back up.

Can this be an overheating issue? I've heard before that if the CDI box overheats it can cause this, but I don't want to spend 60 plus dollars on a new CDI box just to test a theory. Riding for a while will casue the engine to get too hot, and also make the CDI too hot since the CDI box sits right above the engine. 

If its a carb issue, maybe the carb gets flooded when I slow down too fast, and its hard to start because of that flooding? Should I try leaning out the pilot air screw?

 

thanks!

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I had the same problem on my xl500s. Same year. I did just about everything rebuild the carb , running lean In the end I ended up having to replace the cdi. But after that it became one sweet machine Try adjusting the carb for flooding but I have a feeling about the cdi

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I had the same problem on my xl500s. Same year. I did just about everything rebuild the carb , running lean In the end I ended up having to replace the cdi. But after that it became one sweet machine Try adjusting the carb for flooding but I have a feeling about the cdi

 

Thanks for the help!

 

So you think it was running lean AND the CDI was bunk? I changed the setting on the air/fuel mixture screw a bit (turned it a bit clockwise), and it seemed to help it a bit. How did you do to richen it up- did you rejet the pilot, needle, or main? Or did you just adjust the air mixture screw?

 

About the CDI- I can't find an OEM or used one anywhere. Do you remember where you got yours?

I found this aftermarket CDI from Europe, but its a bit pricey. 

 

Thanks again.

 

Sina

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I rebuilt the carb the float was sticking a bit and I adjusted the mixture screw 5-6 times trying to get it steady where I like it. That helped a lot.

Are you loosing spark? That's a good sign it's the cdi

You can use a volt meter to check continuity from the cdi to ignition coil to the spark plug.

I replaced the spark plug wire with a new f150 ford wire it works great

As for my new cdi. I looked for 3 months I emailed a dozen or so parts yards. Found one in Illinois that had one. I suggest watching eBay for it. And the xr500 uses the same cdi just different carbs

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So I turned the air/fuel screw in about half turn clockwise. Seemed to help a bit

 

I'll tackle the carb this week, maybe go up a size for the main jet. The annoying this is my carb's air/fuel screw has some weird limiter cap on it. Sounds annoying to adjust.

 

Another thing I noticed- After riding for a long time (freeway speeds for about an hour), there is a loss of power and an odd engine sound when I pull on the throttle to accelerate. Sounds like a "click-clacking". The bike doesn't die or anything, it just emits the sound and loses power.

 

Do these bikes come out of the factory too lean or something? If theres a suggested re-jetting spec I'd be happy to do it.

 

Thanks!

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I'm not sure about the clacking but You might wanna check the spark plug at higher speeds it'll lose acceleration if its not gapped right. Mine at least does. The ngk needs to be 0.6mm or 0.025 -0.027 inch There's also this ImageUploadedByThumper Talk1440181170.779205.jpg

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ImageUploadedByThumper Talk1440181830.421369.jpg

It may need adjusting here's how. Might have something to do with the clanking

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Also I don't know if this matters but the XL is running on 10W-40 fully synthetic oil

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10w40 is right no problem there. And For plugs. I use ngk In everything I don't thing there's much difference in how they preform just how long iridium lasts vs standard(copper)

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0_0.png1_0.pngAir cut-off diaphragm #12 can cause weird stuff like you are experiencing.Very gently, hold it towards the light and see if there is a split in it.

Edited by Muzz67

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Interested to know if you have made any progress?

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With ngk spark plugs the lower the number, the hotter! So say it is a BRE6A! A BRE7A would be colder!

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Have you checked the reeds? ;)

As a side note, for the rocker arm pins, you can drill a small hole in the top of the rocker cover above the pins and knock them out with a small pin punch. It's very common practise and does the job perfectly.

Just fill the hole above with a little silicone or other desired sealant once you're done.

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Have you checked the reeds? ;)

As a side note, for the rocker arm pins, you can drill a small hole in the top of the rocker cover above the pins and knock them out with a small pin punch. It's very common practise and does the job perfectly.

Just fill the hole above with a little silicone or other desired sealant once you're done.

 

Thanks!

I would still have to remove the rocker arm cover in order to do this, yes? The issue is the Clymer manual states the engine must be removed in order to allow proper clearance to remove the cover. I've heard I can just try and lower the engine a bit in the frame to do so.

So drill in directly from the top of the cover in order to contact the rocker (with a drill bit smaller than the dowel pin, yes?), and after installing new dowel pins I would be able to fill the holes with something like hondabond HT?

I've also heard to replace the rocker arm shaft O-rings with non-standard ones (green o-rings that can be found at a bearing shop). 

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I just ordered a custom aftermarket CDI from Europe:

http://www.rexs-speedshop.com/Honda-XL250-XR250-XL500-XR500-CDi-Unit

 

When I get home, I'll install it and see how it runs. I'll report back later.

 

On a side note, what seemed to really help the engine dying was when I cleared out the fuel tank breather hose/cap. It was a bit clogged and it was causing too much negative pressure in the tank, making it starve for fuel. 

 

I'm also going to try and richen up the main. I think standard main jet is 155? Any recommendations on what jet size(s) I should get?

 

Thanks!

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