Completely stock bike running hot

[xs650newb]

Hey all,

My 1977 XS650D is running way to hot.

I went on a 15 minute intown ride. Rarely broke 3K rpm and kept it under 40 mph. It is about 85 degrees out right now and my wife was on the back. The plugs are white with a faint hint of brown. Definitely too white for my taste though. Also, I took some temps after the ride.

Top of crankcase (near where you put in oil): 220
Head near right spark plug: 280
Pipes as close as possible to exhaust port: 390

The bike is (almost) completely stock. I recently cleaned carbs (stock jetting), set the camshaft tension, and set the valves.

A also searched for air leaks and couldn't find any. My method was to spray wd40 in various places and look for a change in revs of the bike at idle.

Here are some caveats:

1) The airfilters were rotted out so I removed the old foam and put in new unifoam foam and glued it to the metal skeleton of the old air filter.


2) The bike run Ok and starts GREAT. It starts within 1 revolution using the electric starter or with a single kick. I choke it for 5 seconds then turn off the choke and ride off.

Runs great initially then I feel a slight surging once it is warmed up and it will bog down if you crack open the throttle. It accelerates real quick after bogging down for about 1 second.

Any ideas whats going on?

Best,
Adam

 

[jd750ace]

Surging is lean. Bogging on opening it up is lean. White plugs are lean. I'm just guessing you're lean. Go up at least one size on the pilot and the main. The Uni foam may flow better than what you had. Also, is your air box air tight around the side plates? if not, this allows in more air than stock jetting was set up for.
Just my shade tree thoughts.

 

[5twins]

Until you get larger jets, you might try setting the needles a step richer. The '76-'77 carb set came with the smallest mains ever put in the 650, 122.5s. They work fine on a totally stock machine but any type of mod can quickly out pace them. Your air filter "upgrade" may be doing that.

 

[xs650newb]

Thanks guys.

Is it possible to still purchase stock air filters for the 1977? I'd defininitely purchase them if I could find them. So far, I've only seen NOS and I can't imagine the foam is still good.

Additionally, my airbox has one or two holes that have been taped over. I'd definitely like to get an original airbox without any issues. Will the airbox off of a 1978 fit the 1977? There is one on ebay right now for a great price.


I'd like to bring my airbox and airfilter back to perfect stock condition before I start playing with jets.

I noticed when I first got the bike that each airbox actually had two air filters. There was the airfilter that was right behind the carburetor that has the metal skeleton and there was another air filter, completely foam, behind it. Currently, I only have the metal skeleton air filter because the all foam filter disintegrated when I touched it. Can I purchase/replace that second air filter?


Best,
Adam

 

[5twins]

I never heard of a second air filter, unless it's #24 in this drawing, what Yamaha calls a "Silencer" .....

http://www.boats.net/parts/search/Yamaha/Motorcycle/1977/XS650D/INTAKE XS650D/parts.html

It was only used in '76 and '77. Yes, a '78 airbox will work, but it won't have that "Silencer" foam. Yamaha stopped using it so I doubt it's critical to have it in there. Apparently it's not filtering air, just quieting intake roar.

It appears air filter elements are still available, if you don't mind spending $60 or $70. Frankly, I don't see the point. What you've done with the UNI foam is perfectly acceptable. Now you just need to tweak your carb tune to match. You're going to have to learn stuff like this if you expect to keep an old bike going without it putting you in the poor house, lol. Properly tuned with freer flowing air filters and slightly larger jets, your 650 will perform better than stock.

 

[xs650newb]

Hi 5twins and others,

Yes, it is part #24 in that diagram. Looks like I can ignore it. Thanks for the info.


So I went through my airbox last night. Completely removed it from the bike, checked it for leaks, and re-installed. I was very careful on the re-install and everything is nice and snug.

I put in new plugs and went for a quick ride. Kept the bike under 3K rpm except for a few very short bursts.

The plugs are still white!


I went and ordered some larger pilot jets from 650central. Additionally, I ordered the stock airfilters for this year. My plan is to first put in the stock airfilters and see if the situation is improved. If not, I'll go up one size on the pilot jets.


I didn't purchase main jets because I never really cracked open the throttle to a high enough rpm range where the main jet would come in.


Also, what is the stock position of the needle clip? I'm going to check that and make sure its stock. Also, when does the needle jet play a role? i.e. in what rpm range.

Best,
Adam

 

[weekendrider]

http://api.viglink.com/api/click?fo...um&txt=http://www.amckayltd.com/carbguide.pdf

This will be a helpful read. It answers those exact questions and more.