Jump to content

1987 XR600R starting issues

Recommended Posts

Just tightened my valve lash to spec after having terrible clacking noise when idling. It would start before when cold with no choke at all but would click and clack when idling. But now, with the correct valve adjustment, the engine does not want to start. It will backfire and damn near break my foot so I know that it is definitely getting fuel. What is the best way to adjust the carburetors on these bikes? I know there is the large screw on the right side to adjust both of the slides for idle speed, but where is the air-fuel mixture screw on the carbs? I suspect this is my issue now that the valve lash is adjusted correctly. Any info or advice would be greatly appreciated. 

17761345_10211664181507264_942325671_o.jpg

Share this post


Link to post
Share on other sites
Just tightened my valve lash to spec after having terrible clacking noise when idling. It would start before when cold with no choke at all but would click and clack when idling. But now, with the correct valve adjustment, the engine does not want to start. It will backfire and damn near break my foot so I know that it is definitely getting fuel. What is the best way to adjust the carburetors on these bikes? I know there is the large screw on the right side to adjust both of the slides for idle speed, but where is the air-fuel mixture screw on the carbs? I suspect this is my issue now that the valve lash is adjusted correctly. Any info or advice would be greatly appreciated. 
17761345_10211664181507264_942325671_o.jpg.938debbfe41fe5bda32e45858098e508.jpg

Air screw is on the left side kind of near the fuel inlet.

Share this post


Link to post
Share on other sites
9 minutes ago, Backwoods-Bomber said:


Air screw is on the left side kind of near the fuel inlet.

What is the best way to set the air screw? all the way out with choke on then in until it idles without choke? Is there only one air screw then?

Share this post


Link to post
Share on other sites
What is the best way to set the air screw? all the way out with choke on then in until it idles without choke? Is there only one air screw then?

Yes, only one air screw. Its on the primary (left) carb.

 

Clean air filter, air screw all the way in then backed out two full turns. warm up the bike, no choke after initial startup.

 

Once warm, make all adjustments with the bike running. While counting turns, turn the screw in or out until you find the fastest idle speed. Now turn the screw in (richer) until you hear the idle speed drop by about 100 rpm, basically until you can hear a noticeable drop in idle speed. Now use the idle speed screw to set the idle to about 1200rpm. Done.

 

After this process your air screw should end up between 1 and 3 turns open. If you're out of that range you need to change pilot jet size.

 

 

 

  • Like 1

Share this post


Link to post
Share on other sites
3 minutes ago, Backwoods-Bomber said:

Yes, only one air screw. Its on the primary (left) carb.

 

Clean air filter, air screw all the way in then backed out two full turns. warm up the bike, no choke after initial startup.

 

Once warm, make all adjustments with the bike running. While counting turns, turn the screw in or out until you find the fastest idle speed. Now turn the screw in (richer) until you hear the idle speed drop by about 100 rpm, basically until you can hear a noticeable drop in idle speed. Now use the idle speed screw to set the idle to about 1200rpm. Done.

 

After this process your air screw should end up between 1 and 3 turns open. If you're out of that range you need to change pilot jet size.

 

 

 

Ok I will follow this exactly. Could the air screw being set incorrectly be causing the no start condition I am having? 

Share this post


Link to post
Share on other sites

It could be, but carb adjustment and valve lash are pretty much unrelated. I would double check valve before messing with the carb too much. Are you sure it was at TDC when setting lash?

Valves too tight can create the starting issue you describe. If your carbs were fine before, I would assume they probably still are.

Share this post


Link to post
Share on other sites
4 minutes ago, Backwoods-Bomber said:

Has it run at all after the valve adjustments?

It has not run no. It has tried to run but hasn't gone into an idle. I did my valve adjustments right at the top of the compression stroke right before the intake valves were supposed to open just like the manual says to. That is the only thing I've changed since it doesn't want to run though so I must have did something incorrectly. Should I try the small dowel in the spark plug hole trick to make sure it is at TDC and do it again? I also set the valve adjustments to the lower end (tighter) of the allowable limit instead of the upper end (looser). 

Share this post


Link to post
Share on other sites
I did my valve adjustments right at the top of the compression stroke right before the intake valves were supposed to open just like the manual says to.


This would put it on the exhaust stroke, not compression.

It should be the top of the stroke following the closing of the intake valves.
  • Like 1

Share this post


Link to post
Share on other sites
2 minutes ago, Backwoods-Bomber said:

 


This would put it on the exhaust stroke, not compression.

It should be the top of the stroke following the closing of the intake valves.

 

Ok so the valves are too tight now? When I am turning the engine over as soon as the intake valves close and when the TDC mark is visible through the hole, thats where I set the valve lash? Should I set them to the tighter or looser end of the feeler gauge?

Share this post


Link to post
Share on other sites
Ok so the valves are too tight now? When I am turning the engine over as soon as the intake valves close and when the TDC mark is visible through the hole, thats where I set the valve lash? Should I set them to the tighter or looser end of the feeler gauge?

Yup, and a dowel down the plug hole is a good trick too.

Valves tighten as they wear so I go with on the looser end, but just barely.

Share this post


Link to post
Share on other sites
1 minute ago, Backwoods-Bomber said:


Yup, and a dowel down the plug hole is a good trick too.

Valves tighten as they wear so I go with on the looser end, but just barely.

Ok sounds good, I will do just that. Should I even look at the carbs before I readjust the valves or should I just see if that fixes my issue? My brand new plug was a good sooty black after a 30 min ride last weekend. Thanks for all the help by the way. 

Share this post


Link to post
Share on other sites
Ok sounds good, I will do just that. Should I even look at the carbs before I readjust the valves or should I just see if that fixes my issue? My brand new plug was a good sooty black after a 30 min ride last weekend. Thanks for all the help by the way. 

No problem! Fix the timing first. Once it's running like it used to (but hopefully quieter) then move on to carb adjustments.

Share this post


Link to post
Share on other sites
Just now, Backwoods-Bomber said:


No problem! Fix the timing first. Once it's running like it used to (but hopefully quieter) then move on to carb adjustments.

Ok willdo. Also before I tried to adjust the valves it wouldn't EVER start if it was hot. It would run awesome for a 20-30 min ride in the woods but if I killed it going up a hill or something you bet I was pushing it home. Could that have been the intake valves being too tight once it warmed up and not letting enough air in? Or does that sound more like a carb issue?

Share this post


Link to post
Share on other sites

My 87 XR 200 valves were, per the manual, to be adjusted when cold.  .002 for the intake and .003 for the exhaust if memory serves me.  Make sure you check the gap again after you tighten the lock nut.  The feeler gauge fits between the adjuster and the top of the valve stem.

Share this post


Link to post
Share on other sites
Ok willdo. Also before I tried to adjust the valves it wouldn't EVER start if it was hot. It would run awesome for a 20-30 min ride in the woods but if I killed it going up a hill or something you bet I was pushing it home. Could that have been the intake valves being too tight once it warmed up and not letting enough air in? Or does that sound more like a carb issue?

Valve gap is not not a matter of the valves letting enough air in, it's about making sure there is no pressure against the valve holding it open when it's supposed to be closed.

The hot restart issue is probably separate imo. I would expect rich jetting or possibly an ignition issue.

Share this post


Link to post
Share on other sites

UPDATE: Valves adjusted correctly. Rode around for 5 mins and was able to adjust the idle screw but it died afterwards. kicked for a few mine before pulling plug and discovering i lost spark. new coil and stator have been ordered already, hopefully that fixes it for good. 

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×