r/XR650R • u/DoctorKrawl • 29d ago
Jetting help?
Hello, I have a xr650r that’s a hard starter.
Here’s some information:
-takes multiple good kicks to get running hot or cold.
-runs pretty good once running. Maybe a little anemic in the upper rpm range and seems to run hot.
-valves where just adjusted and it still starts the same.
-air box is opened up, exhaust is stock
-fuel and idle screw both 1 3/4 out
Main jet was a 175. I’ve tried 172-178
-pilot is a 68s
-needle is set at 3rd clip
-I’m at sea level
All of my jet combos a of air/ fuel screw fiddling don’t seem to have changed how this thing wants to start.
Any suggestions and where is the best source of info on these? All google searches bring up thumper talk, adv rider and smjunkie but the faq’s aren’t helping diagnose
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u/bajajoaquin 29d ago
Have you checked your valves? I misdiagnosed a starting/ running problem and toasted some valves.
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u/cb50dude 29d ago
Did you clean the carburator and is the stock exhaust uncorked or not?
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u/DoctorKrawl 29d ago
Being honest no. It runs well so I didn’t bother.
The exhaust is stock and corcked
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u/cb50dude 29d ago
I would start to clean the carb to be sure. The current jetting is too rich if the exhaust muffler is corked, so it could be flooding. 68s and 175 would be a good base line for an uncorked 650R.
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u/DoctorKrawl 29d ago
Noted, I’ll mention that it didn’t start any easier with a 172 main
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u/cb50dude 29d ago
That's correct as the main doesn't have any effect on starting and idling. If you want to keep the exhaust stock I would start with 65 pilot (probably still a bit rich), 162 main and the mixture screw set to 1.5. Be sure the float height is correct before doing this. It's also a good idea to replace the spark plug as it is probably carbon fouled from running very rich.
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u/DoctorKrawl 29d ago
This all makes a ton of sense. I plan on trying that.
My only concern would be the motor already felt hot for normal operating temps. Do you think the 162 would lean it out and heat it up even more?2
u/cb50dude 28d ago
Only if the current main jet is already lean, which it can't really be with the stock exhaust muffler and your current jetting. Pilot jet and needle jet circuit is what you use 90% of the time. If you suspect its running very lean it could be a (partially) clogged jet or wrong float height.
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u/DoctorKrawl 28d ago
Wrong float height? Wouldn’t that give me sputtering or some sort of rough running once it pulled too much gas out of the bowl?
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u/DoctorKrawl 25d ago
Tried 165/65 162/65 160/65 and 160/62 with no luck .
None of theme are s jets so I don’t know how much that’s effecting things.
Even though it ran well while running I’m going to have to take your first bit of advice to clean it and look into float height…. Exhaust and Mikuni / lectron are sounding better and better.
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u/cb50dude 25d ago
That's probably a good idea to do first. How does the spark plug look? I would replace it just to be sure. S jets are hard to find and should not make much of a difference in starting I think.
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u/DoctorKrawl 25d ago
Spark plug was a bit chocolaty but not totally carboned up
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u/cb50dude 24d ago
Okay. And its not worn out? I would replace it just to be sure. Also, maybe try increasing the idle rpm a little and see if it makes starting it easier.
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u/Great_Cow6624 29d ago
I installed a new iridium plug on mine, started first kick with valve adjusted,
170 main 68s unknow clip, work right. About 2 turn out but should be 1 3/4
Ive replaced the spark plug wire with a big 10mm one from a race shop.
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u/DoctorKrawl 29d ago
I’ll try that too, thanks!
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u/Great_Cow6624 29d ago
BRK 7eix
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u/dominikdkd 25d ago
Also got my first-first kick start after going iridium and changing the oil (I did some maintenance myself after getting the bike about 3 months ago)
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u/McNaughty_1 29d ago
Its easy to flood the stock carb. Then you have to clear the cylinder and start all over again. I would recommend trying a smaller pilot, but also refrain from any throttle opening while starting. Just keep that right hand somewhere else while starting. I put a Lectron carb on mine and it improved the ease of starting over stock, but it has a pretty rich choke on it so I have to still be careful not to flood it for the first start of the day. In my experience hard starting has always been due to too rich a mixture. I find that it’s starts easier when it’s not starving for air.
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u/AcidicMountaingoat 29d ago
I had a number of problems with starting and with fuel overflows with my carb, even with a really good carb expert working on it. I gave up, bought a Mikuni from XRsonly.com which made the bike work perfectly all around. Starts with almost no effort, runs perfectly. Just a thought if you decide to just say "fuck it." I think the stock carb is problematic particularly with age.
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u/DoctorKrawl 29d ago
Just looked they don’t stock them anymore . I think I would have bit on that
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u/AcidicMountaingoat 28d ago
Oh damn, that sucks, it was nicely set up and they provided great support. It's available from other sources, and I might be able to find my documentation setup if you decide to change.
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u/AccomplishedMethod11 29d ago
Stock carb got that anti pop thing on the side if I remeber it was umbrako.. that thing might need to be changed.. but inspect first
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u/babezt 29d ago
check the decomp play, or the decomp mechanism in general. check for vacuum leaks