'00 Yamaha WR 400F hot starting issue

[AteszTG]

I've got a 2000 Yamaha WR 400F, I've got it since last year december, since then, the motorcycle was fully disassembled. The chassis was painted, and the engine was at a mechanic, who adjusted the valves inside the engine, and changed the chain inside the engine. He wasn't had the carburator, only the engine. So, we're (me and my father) on the same thing, the engine doesn't have any problems, 'cause it was fully remade. The problem started on the previous weekend. We've put together the whole motorcycle again, and as it was cold, on the first kick we've managed to start it. We both was very excited and happy, 'cause it was actually working! The problem started after the first startup. As the engine was running for about 5 minutes or so, we stopped it, and wanted to restart it, just to make sure everything is in order, and works have it supposed to, we wasn't able to acutally re-launch it (as time went on, we managed to learn have to kick the bike in). After a little cold down, we was able to start it up again, and so, we've gone out for a quick test ride, near the fields. Everytime, when I've stalled, I was able to kick the bike back in, and start it up. Every single time. But, when we've decieded to take our way back home, after a little break, we wasn't able to start the bike back, so we pushed it back home. As we later noticed, we've fully disable the gas tap, and it managed to stop our problem. This week monday came along, and me, alone managed to ride outside. First kick, it started. Like with no problem. On the start, I stalled it, and after I was able to kick it back again. I've put it in to 1st gear, and ride out, for about 5 minutes when I've stalled again. After that, I wasn't able to kick back in, for like 10 minutes till it have cold down. We was thinking about, what could be the problem. Today, we've changed the spark plug, to a new original spark plug. The engine now is running a bit better, but still, when it gets hot, it won't start up to the second time. It always starts up after you've shut it down, or stalled it, but never for the second.
We've got one well known problem, which is the left side radiator. It's leaking, but not much. You actually lose like a spit liquid from both radiator after a 10 minute ride. We need some help, please!

EDIT: Soo... other problem came up just right in this moment. In the moment, I was writing this message, my dad was working outside, and somehow he managed to "break" the kickstarter, or something. It won't return, just simply with helping it with a hand. Maybe spring slipped down, or it've broke? My dad saied, it clicked when it started happening. Is it safe, to start up with this problem, or what shall we do with this too? I'm getting tired of finding to many issues...
EDIT2: We're talking about the things that have happened this afternoon, and as my dad saies, he saw that the gas filter was nearly or fully empty. This time, he removed the tube between the filter and the carburator, and no fuel was coming out. He plugged it back, and he removed second time between the filter and the gas tap. It was leaking fuel from the tube, so he quickly plugged it back, and as the filter filled up, he removed the tube between the filter and the carburator and it leaked, not like previously... we don't know why again. There was the some gas tap-gas filter problem, on the first ride that we've done together with my dad, and the second ride which I did alone... Soo... maybe everything is with the gas pumping or some s!#t....

Sorry for the hard explonation, but I'm not actually english, and it's hard to me to write about engine stuff, with a little knowledge, but in my country, I wouldn't get any help, on any forums. So, I hope you guys can help us! Thank you.

[jaffa90]

Does this bike have a HOT START pull knob and a DECOMPRESSION LEVER to aid starting ?
Are you using the CHOKE on a cold start ?
The kick start broken bits needs sorting first.

[P.]

Should have auto decompression on the kick start.

Hot starting usually means valves need adjusting.

[Meatybeaty]

Download this manual it's multi-lingual
https://www.manualslib.com/manual/582271/Yamaha-Wr426f-N.html

[-]

There was a difference between the WR and YZ 4T's where the exhaust cam is set one tooth differently for a more aggressive MX style response.

Some WR owners used to do this then a couple of other mods to turn it basically into a YZ400F.
If this is possible, it might have been done by accident and require other mods to work properly.
The other mods I remember, were a throttle stop screw and a wire somewhere around the ECU which you could attach a switch to and basically change the ignition curve from WR to YZ whenever you wanted.
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[Copycat73]

valve clearances .. and the fact it's been it allegedly already been done by a mechanic means nothing till you put a feeler gauge in..
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[AteszTG]

[P.]

[AteszTG]

Okay, thank you guys! Tomorrow, we will take a look at the valves! I'll reply when we've managed to learn something new. Thanks a lot, really!

[AteszTG]

Alright guys. We're working on the damn thing all afternoon, and all morning to make it run smootly. We checked, as you guys mentioned, the valves. The valves are clear, and setuped very well, so there couldn't be any issue. We take down the carb, for making it sure everything is good there too, we made it clean from the gas, so actually we haven't done nothing, just took it apart, and check if everything is okay, but it was! Valves are nice and clean, gas is flowing from the tap, carb is clean, and it works have it supposed, so we don't actually know nothing! We haven't start it up, beacuse of the broken kick starter, but as 03/11-12 comes, we'll be able to replace the spring, so we'll be able to make it run again.
Can it be any problems with the carb setup actually? Because, when you're going like, in 1st gear, around 4-5k RPM, if you made it drop to 0 RPM, and pull in the clutch as fast as possible, to make the engine's "resistence" (idontknow how to explain) less, it kills it. It dies. And you're not able to hot start it again.. Some as in idle. Yesterday, we've idled it for like 3-5 minutes, to make engine hot, and after trying to restart it, it don't... It couldd be with me, beacuse I know, I should aply some throttle, when I want to pull in the clutch but hey... the problem is still up, hot starting is not a thing on this bike.. with nice valves, spark is good, we've checked the plug, and replaced it to make sure, spark is good! Anything else, is only the carb.. or could be something else? We need help..

[P.]

What are your current valve clearance measurements?

Its either going to be valves or carb, but less likely the carb.

[struan80]

I'll get my coat if I'm wrong but is it he cannot have checked all of these things without starting the engine, which he can't because of the broken kickstarter? It's a question not a statement guys.

I like riding, fixing things are for when I can no longer ride.

I'm right now going to read up on valves.

Hope you get your bike sorted mate.

[P.]

Only hot starting issues I've had were on a Ninja with incredibly tight valves when it was hot, freezing cold day it would fire up, get it to operating temperature and it was a fucker to start.

That and on an RX8, but that is because the engine is a consumable.

[Robby]

Valve clearances and carb settings need to be checked. You need a workshop manual.

For the carb, it needs to be clean and it needs to be properly adjusted. This means checking/adjusting the following:
- Float height
- Needle position
- Mixture screw position
- Idle screw position

If any of these are slightly wrong it will still work, but give you problems. The problems could be low power, trouble with hot starting, trouble with cold starting, or idling.

[AteszTG]

So, setting up the valves, and the carb, I can find it all in the workshop manual, that was linked earlier?

[Meatybeaty]

Yes , it's all in that manual

[AteszTG]

Okay.. as we talked about with my dad, we'll put it back together, and as we've read in the manual, we going to start up when it's hot, like it says. And if it fails, same. If fails, idontknow what we'll do. The next time when we'll work on it is on the weekend, same as with the riding.. So, I'll update the situation on the next weekend. Thanks for everything guys.

[Fizzer Thou]

It sounds like the kickstart return spring has broken.Easy enough to replace as I have done one on a friend's WR

https://www.fowlersparts.co.uk/parts/4166568/wr400f-5gs6-2000-060-a/starter

As for the starting once hot,these bikes are notorious and even the 426 was no easier.Not good when you are stopped in the middle of a deep puddle and no one will jump in to help to push you out....

A friend had a new late model WR450F with the FCR carb and it was a pig to get to run correctly once a free flowing exhaust was fitted (the standard one gives far too much back pressure and this causes many problems but is part of noise restrictions that Yamaha try to comply with).
The throttle stop screw was replaced for the YZ version and the needle was changed.Various main jet combinations were tried and still it would not run correctly,which was frustrating for the owner as he was unable to ride and race with us.The grey wire was cut but this did not change things to his advantage.

In the end he sold it and bought a new WR250F instead.
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[AteszTG]

Hi guys again! Sooo, my package still hasn't arrived, so I'm waiting for the spring for the kick starter, but till than! We've checked the carb, to make sure everything is good there, we made it clean and I've read after typical issues that accures with the carb on this motorcycle, and I've found actually 3 or so videos whichs shows, that there's a little spring, and a black thing that turns in the accelerator pump when you turn the throttle (so the adjustment screw) (https://thumpertalk.com/applications/core/interface/imageproxy/imageproxy.php?img=https://www.ttbomb.com/z400/fcr/accel%2520pump.jpg&key=eb173282c2162d24fc43d3026bd401e0385d990a3f3962da363dafb3bd43f988 this picture), and as we managed to find out, the bigger piece of the black and the smaller piece, on which is the spring (so sorry for the bad explonition) is not moving instantly, just very slowly when you pull or realese the throttle. So we've fixed it, like it was shown on some videos. Will it help with anything? Like, the hot start issue or the issue that shows up when riding, will any of these two will be fixed?
EDIT:
Also, we had the valves setup correctly as I toled you guys earlier, shouldn't be anything else in the carb? You know, jetting it up, make the mix more richer or cheaper? 'Cause this is the only think we can think of rn, but we haven't found any screws which could set the gas or the air capacity. Could you help us out in that?

[AteszTG]

The engine was overheating, we managed it's problem and now it runs more than fine! Thank you for everything!

[-]

Why was it overheating? Just curious.
____________________
TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.