Help1986 XR80 wont start and idle

[psalas3]

I am a newbie to TT and need some assistance with my son's 1986 Honda XR80. The bike ran well with the exception of smoking really bad when it was running. To keep the EPA and neighbors happy we changed the rings and gaskets in order to resolve the smoking issue. All went well with the ring replacement and reassembly. Once we put it all back together, we were unable to get her started. I have read many of the threads and followed the advice regarding the carb. I have removed the carb and cleaned the jets, bowl and checked the float. All were fine. We have turned both the air and fuel mixture screws all the way in and backed the air screw out 1 1/2- 2 1/2 turns and the fuel screw out 2 - 3 turns. On a few occassions the bike acted like it wanted to start and as I held the throttle all the way open it did run. It started to sputter at first then the idle increased and I was able to release the throttle a bit but it would not idle. I have checked all the gaskets for vac leaks but all are well. I am at wits end and my son is beginning to lose hope for every riding his XR again. Does anyone have any ideas or suggestions? Any assistance will be greatly appreciated.

[theraymondguy]

Valve adjustment.

Set valves to .002" as per manual, I like 'em loose at .004" snug.

Set air screw 1 1/2 turns out, make sure the pilot and main jet are clean. Should run sweet.

[psalas3]

Will I have to pull the motor to adjust the valves. Sorry if it's a dumb question. Working on bikes is kind of new to me. Any recommendations on how to best adjust the valves? I appreciate your help.

[theraymondguy]

Will I have to pull the motor to adjust the valves. Sorry if it's a dumb question. Working on bikes is kind of new to me. Any recommendations on how to best adjust the valves? I appreciate your help.

http://www.cmsnl.com/honda-xr100r-1986-usa_model7713/partslist/E++02.html

Won't have to pull the engine

Adjust your valves. Engine should be dead cold.

Remove spark plug.

Remove the rocker cover & magneto (flywheel) cover. Look for obvious damage to timing chain or cam sprocket, loose or missing valve rocker adjustment locknuts, movement in chain pins etc.

Locate the timing mark on the engine, near to the flywheel (a sharp v cast into the case, will line up directly with magneto). Locate the 'T' mark on the magneto.

Rotate engine using magneto (CCW only), until the intake valve opens (carburetor side), then close; continue to rotate the magneto until the 'T' mark lines up with the mark on the engine case. You should see an "O" on the cam sprocket at the 12 O'clock position, if not exactly 12 O clock or just marginally to the right, your valve timing is off.

At this point, both rockers should have some movement, you should be able to shine a flashlight into the spark plug hole and see the piston. Set the gap to .002" on both valves - a light amount of drag on the feeler gauge is perfect. Check & recheck tension on the rocker adjustment nuts. You should be just able to feel vertical movement on the rockers and here a light 'click' as you move them up and down if all is well.

Make sure the adjustment nuts are tight, reassemble valve cover, kick, ride.

[psalas3]

Many thanks. I will give it a shot tomorrow. Thanks so much for your time and advice. I'll let you know how it goes.

[wanawakeboard]

while your at it check your valve timing... make sure when your at tdc your valves are in the right position in relation to the crank.

[psalas3]

How do I confirm and adjust valve timing?

[wanawakeboard]

there is a notch on your flywheel, and case down below,(to line up) and a dot on your cam gear, Im sorry youll need to research the marks on your particular bike but its possible you got the timing off during assembly...

https://www.thumpertalk.com/forum/archive/index.php/t-349001.html

just do a search on cam timing I havnt had to mess with my 80 yet.. good luck

[theraymondguy]

How do I confirm and adjust valve timing?

"Locate the timing mark on the engine, near to the flywheel (a sharp v cast into the case, will line up directly with magneto). Locate the 'T' mark on the magneto.

Rotate engine using magneto (CCW only), until the intake valve opens (carburetor side), then close; continue to rotate the magneto until the 'T' mark lines up with the mark on the engine case. You should see an "O" on the cam sprocket at the 12 O'clock position, if not exactly 12 O clock or just marginally to the right, your valve timing is off."

[psalas3]

Thanks you both for your help. It appears that the cam timing issue kept the XR80 from running. Now that it runs may I pick your brains for carb tuning advice? What are the correct setting for the air screw and the fuel screw? I have read 1 1/2 for the air screw but not quite sure about the fuel screw. The bike will run for a bit and idle at a good speed then die out after about 3 or 4 minutes. Any ideas?

[theraymondguy]

Thanks you both for your help. It appears that the cam timing issue kept the XR80 from running. Now that it runs may I pick your brains for carb tuning advice? What are the correct setting for the air screw and the fuel screw? I have read 1 1/2 for the air screw but not quite sure about the fuel screw. The bike will run for a bit and idle at a good speed then die out after about 3 or 4 minutes. Any ideas?

Looking at what should be the OE carb...

Sounds like you may be running out of fuel...

Check your float height;

- The easiest way to check float height, get some clear 3/16" fuel line attach it to the drain spigot on the bottom of the float bowl. Park the bike on a level area, then level it side to side so it's as vertical as possible. Loop the line you just installed so it runs in line with the throttle valve and tie wrap it in place (line should be the shape of the letter 'J'. Open the drain screw on the bottom of the carb (a small amount of fuel make leak out of the drain screw, be prepared). Fuel should enter the line, but should go no higher than the top of the float bowl (if it does your floats are sunk or you have an issue with needle/seat). If all seems well fire the bike up and let it idle till it dies out; monitor the fuel level in the line.

Did the fuel level lower when the bike dies? If so, you're running out of fuel. Check for an obstruction (plugged tank filter, plugged fuel line, poorly routed fuel line, valve in gas cap plugged or breather line plugged).

As far as carb adjustment goes, assuming you have the original carb...

the screw closest to the intake manifold is the air inlet screw; should be ~ 1.5 turns out from softly seated (don't crank it tight, you'll damage the seat and ruin the carb). The screw toward the center of the carb is the idle screw, set it so that the bike idles at a reasonable speed. Get it good and hot, then adjust the idle screw in 1 full turn (idle should increase) then adjust the air screw .25 turn in, then .50 turn out. Find the spot where it idles the highest, and back down the idle screw until it idles at a reasonable speed.

[psalas3]

Thanks to all of your help I think I got her fixed. I may have the fuel lines goofed up. Can anyone confirm which line goes where? A schematic would be helpful.

[theraymondguy]

Fuel line from tank goes to brass spigot on top of carb, on left side. Remaining lines are for drain and overflow, just hang them out of the way and toward the ground.

[psalas3]

One last question. Does the fuel line go to the brass spigot on the top center of the carb or on the spigot further back just above the bowl. They are both on the left side of the carb.

[psalas3]

Thank you theraymondguy and wanawakeboard. I finally got the XR80 running. My son and I are very grateful of your time, knowledge and patience. We appreciate your help very much. Let me know if you ever come down to San Antonio. Ill buy you both a beer.

Thanks again.

[theraymondguy]

Thank you theraymondguy and wanawakeboard. I finally got the XR80 running. My son and I are very grateful of your time, knowledge and patience. We appreciate your help very much. Let me know if you ever come down to San Antonio. Ill buy you both a beer.

Thanks again.

Good to hear! If I'm ever in San Antonio, I'll bring the beer (Canadian stuff, I believe Americans call it 'Whisky').

[socalxr]

Good to hear! If I'm ever in San Antonio, I'll bring the beer (Canadian stuff, I believe Americans call it 'Whisky').

???

[loom34432]

Look at Powroll.com this site is very helpful and full of info on carbs.