TC 250 Hot Start Issues

[DakarSafari]

Hi.
We have a brand new 2010 Tc 250.

The short story is it is very difficult to kick start when hot. I have read a number of threads in here and Thumpertalk that talk about the issue, but none of the threads seem to reach a conclusion, so I was hoping I may be lucky and find someone here who has:

1. Identified the cause properly
2. Made tuning or modification changes to eliminate the problem.

Any help appreciatted.

Ps. The TDC kickstart method is ok, but really only a get around. It is not a respectable solution for race scenarios.

Many Thanks.

Australian model. Sea level racing at 20 to 30 celsius.

 

[john01]

I have an 2010 TC 250 that usually starts on the first kick hot but sometimes it takes 2-3 but no more. We called Hall's and they sent out a few parts, jets, bowl cap, and needle I think. It's been so long ago I can't quite remember what all they sent. Anyway we installed the parts and like I said starting for us has been quick and easy. We do bring the kickstarter to TDC and press through and not kick it like a 2stroke. If you do kick it hard and fast starting is much harder as I'm sure you are aware. I know in a race that would be hard or at least slow but IMO it is what needed to get it to start quickly. I'm use to it now and really along with the carb updated parts really don't have a problem starting. I have read that others changed the cam and something else that helped even more. I'm thinking about a new 2013 TC or TXC but the FI scares me more than the carb on the 2010.

 

[DakarSafari]

John01. Many thanks for sharing your experience. The TDC method could be refined on our side, but i'd really like to get to the bottom of the problem/reason for the hot start failure, then build a solution.

Besides this prob, we love the bike. Beautifully balanced, great ergonomics and power delivery in an Enduro setting

Any help appreciated, especially from Racing Teams.

 

[DakarSafari]

Bump

 

[ray_ray]

I've got 2 of these bikes ... One was a very hard starter, hot and cold ... And I can say that the fix was on the auto-decompressor spring ...I changed the EX cam that has the spring on it and the bike starts very easy now ...

Just do the TDC stuff, slightly crack the throttle before the push-down on the kicker is started (not like a 2t where the throttle is twisted at the same time as the kicker is kicked) , and push the kicker down for 1-3 kick starting ...

Before this new cam and spring were applied, my bike would kick back very hard and often when kicking it over AND when locating TDC, the engine would need to be kicked over numerous (4-5) times before it felt like the compression stroke was found ... If you engine sounds like this, that spring on the cam may be your issue also ... Remember, my bike never started easily and when hot, it was even harder to start ...

Here is some video on what I saw with my bike ..

http://www.cafehusky.com/threads/exhaust-cam-spring.17392/#post-278521


EDIT: It is OK in a race situation if it starts the bike ... It takes less that 2 seconds to find TDC ... But you gotta keep your composure

--

Second bike requires the hot start BTN to be pulled out it when hot it seems but I'll need a few more days riding it to verify this ...

 

[DakarSafari]

Wow! Great feedback.

Ok...So the later cam has a snappier spring and from the video that was posted shows quite a difference in action (frankly the first one has 'no action' really and could be regarded as defective.

This morning I dropped into a machine shop I use for one off jobs. I trust these guys. I showed the video and he was sure he could pop off the pin so we can get at the spring. He also uses a guy to make springs so the conversation went down the path of pulling the pin, making a replacement spring and refitting. Any comments guys?

My followup question is this though: Does the 'new' cam have a different profile too?

Many thanks for all the help so far....i really want to nail this down before the race season starts (we can run the 125 two strokes for the early tight woods races, but I want that 250 super reliable once we start the open racing).

Cheers. :-)

 

[ray_ray]

Wow! Great feedback.

Ok...So the later cam has a snappier spring and from the video that was posted shows quite a difference in action (frankly the first one has 'no action' really and could be regarded as defective.

This morning I dropped into a machine shop I use for one off jobs. I trust these guys. I showed the video and he was sure he could pop off the pin so we can get at the spring. He also uses a guy to make springs so the conversation went down the path of pulling the pin, making a replacement spring and refitting. Any comments guys?

My followup question is this though: Does the 'new' cam have a different profile too?

Many thanks for all the help so far....i really want to nail this down before the race season starts (we can run the 125 two strokes for the early tight woods races, but I want that 250 super reliable once we start the open racing).

Cheers. :-)

Not sure on the profile of the cam and I'm not sure of the mechanics of that auto-decompressor ... Looks like a funky little device to me and I see no way that it actually operates ...

--

Was the action on your de-compressor slow and lazy? You can bent it on the shaft but you need to be careful and get a good straight bend that applies pressure ...

 

[DG Harv Serv]

I have a TC250, bought new in OZ as a run out model . I found it came jetted lean .

I had to Increase the Main Jet (I think to a 185 ? Sorry was a while ago !) and lift the Needle.

Also needed to scew out Fuel Screw half a turn. I removed the lock wire on the Accelerator Pump Lever (Husky Mod ?) and set. Fit an Irridium Plug too.

It starts now first kick cold or hot , if very hot / stalled may take 2 /3 kicks. This is what I do :-

Cold > Choke on, Pump Throttle once, give Kickstart a couple of slow pushes, find TDC, go little bit more then up, give firm quick PUSH on Kickstart, away you go !

Hot > No Choke, No Throttle Pump, then repeat above.

Very Hot > Pull out Hot Start all the way (Has like 2 positions ?), No Throttle, Kick bike 2 / 3 Times quickly .

My bike "Poped and Banged" on the overrun badly (Throttle Shut, Down Hill etc....) and was trickey to start, Now runs great.

Personally I would make sure you have the Basics right before making to many mods !

 

[DakarSafari]

Thanks everyone.

I have looked at the related threads and the video again, as well as the photos in the linked thread. Please correct me if what I say below doesn't add up...

If a cam with 'straight' spring is installed on the bike, bending that spring in the manner shown will decrease the tension and NOT increase it. This will lead to a worse action (look at the way the spring is wound, it would decrease the coil)

My suspicion is that the 'later' spring supplied (with bend) in the new cam, is a tighter spring AND has a different shape....thus giving the required snap.

True????

Of the people reading this thread, who thinks that by changing the cam(with 'new' spring) ..... this will FIX the hot start issues???

Thanx as ever....

 

[DG Harv Serv]

Thanks everyone.

I have looked at the related threads and the video again, as well as the photos in the linked thread. Please correct me if what I say below doesn't add up...

If a cam with 'straight' spring is installed on the bike, bending that spring in the manner shown will decrease the tension and NOT increase it. This will lead to a worse action (look at the way the spring is wound, it would decrease the coil)

My suspicion is that the 'later' spring supplied (with bend) in the new cam, is a tighter spring AND has a different shape....thus giving the required snap.

True????

Of the people reading this thread, who thinks that by changing the cam(with 'new' spring) ..... this will FIX the hot start issues???

Thanx as ever....

I dont think it will "Fix" it , (Make it better ? Maybe ? ) . Personally I would make sure bike is set up (jetting etc...) 100 % first .

I have had 2 x 2010 TC 250s and dont know what spring I have had ! BUT both set up well, Start no problems Hot or Cold !

 

[ray_ray]

Thanks everyone.

I have looked at the related threads and the video again, as well as the photos in the linked thread. Please correct me if what I say below doesn't add up...

If a cam with 'straight' spring is installed on the bike, bending that spring in the manner shown will decrease the tension and NOT increase it. This will lead to a worse action (look at the way the spring is wound, it would decrease the coil)

My suspicion is that the 'later' spring supplied (with bend) in the new cam, is a tighter spring AND has a different shape....thus giving the required snap.

True????

Of the people reading this thread, who thinks that by changing the cam(with 'new' spring) ..... this will FIX the hot start issues???

Thanx as ever....

Maybe ... but like I said.. I have no clue on how that device works, I just noticed a difference in the action between the 2 ...
--

I gave the symptoms of my bike in as good of detail as I could ... If your bike is not acting as mine, I'd leave the valve cover on look at the fuel and CARB..... I was getting kick-back so hard I was afraid I was gonna bust the engine housing if my foot came off the kicker ..

My bike was always hard starting and got a little better, hot or cold, ... This bike had to be massaged before in would start ...

--
Taking that valve cover is easy enough and you can see what you have in there if curious ...

 

[DakarSafari]

Cold start is fine.
Hot start is dreadful. The TDC Method is not at all relable.
The kick from the starter leaver would break your foot without MX boots on!!!

Everything on the bike is stock.

As you can see I'm trying to get to a known cause and known solution point rather than trial/error.

I find it hard to fathom that jetting is the culprit here especially as the bike runs very well when going. Unless there is say massive overfuelling when the bike stops and is hot???

I'd love to hear from someone who knows more about the auto decomp mechanism. ????

The issue must surely lie somewhere in the 'mechanicals' associatted with turning the engine over via the kick start???

 

[DG Harv Serv]

Cold start is fine.
Hot start is dreadful. The TDC Method is not at all relable.
The kick from the starter leaver would break your foot without MX boots on!!!

Everything on the bike is stock.

As you can see I'm trying to get to a known cause and known solution point rather than trial/error.

I find it hard to fathom that jetting is the culprit here especially as the bike runs very well when going. Unless there is say massive overfuelling when the bike stops and is hot???

I'd love to hear from someone who knows more about the auto decomp mechanism. ????

The issue must surely lie somewhere in the 'mechanicals' associatted with turning the engine over via the kick start???

Im not saying you are wrong , and will follow with interest.

But if it was an incorrect Sping / decomp design, wouldn't all 2010 TC250s be the Same ?

 

[DakarSafari]

DG...yes, in theory. Hence me trying to get to the bottom of it (unless the manufacturing process was all over the place).

I'm new to this forum and Huskys. We raced KTMS for 7 years and that has a great informal support forum at KTMtalk.com. We were so lucky in that some serious racers and very knowledgeable mechanics/engineers helped us out a lot so I am really hoping I may be lucky here too. :-)

I guess when I go back to my original post, I was hoping that the issue would be well logged and well understood, with a prescriptive answer coming. :-)

You know.... X jet, Y setting, Z part....bingo****************************************.

As an aside, we rode the very latest KTM SX250F back to back with the 2010 TC Husky (son and I). Price aside, the Husky is a waaaaay better bike for us. Handling and overall setup is beautiful for what we do. We found we had to fight the KTM a little. Hence, I would love to get this Husky spot-on...and pickup a club championship this year.

 

[DakarSafari]

DG...I dropped into my local bike shop (KTM) where I have known the head mechanic there for many years. I thought I would run the situation past him (generically) even though he is not a Husky guy. We bounced it around a bit and this is the essence of what was said.

1. A fair few of the 250Fs and other fours have auto decamp issues, it varies from manufacturer to manufacturer. We spoke about the auto-decomp spring and mechanism and the upshot was we both shrugged our shoulders and said the only way to really know is buy the new cam with different spring and change nothing else. - SO....dead end there.

BUT...

2. He was more interested in the fuelling/jetting. The guidance was this:

a. If the bike starts VERY easily on cold, with no choke and little throttle....then runs well when dead cold and is throttle responsive....then the bike is RICH.
b. From a., even when the bike is HOT, this can lead to excess fuel being present in the barrel at the point the engine shuts off - fouling the plug temporarily - and leading to a tricky re-start.
c. Using the throttle at any time after b., the carb is squirting more fuel in and making a worse situation.
d. At some point c., crosses over from crappy-start to the excess fuel 'exploding/detonating' and leading to the huge misfire and possible kick-back through the starter.

Bottom line is...

Looks like we will lean it out and see where that takes us.

DG.....your instincts are on the money....and I hope the above few bullet points add something to your thinking tooooooo. :-)

 

[DG Harv Serv]

My bike was LEAN when it came from the dealer in OZ . But I dont think 2 Bikes will be exactly the same ?

I am fairly sure I went from a 180 to a 185 Main, Pilot was 42 ? I lifted Needle (dropped Clip down 1 , think was 2 or 3 from bottom).

I scewed out Fuel / Air screw about half turn (2.5 out in total ). Spark Plug I use is NGK Irridium ( from Memory CR8EIX ?).

I then "un wired" the Accelerator Pump Lever (Remove the Black cover over the Throttle Cables on the Carb, you will see a small Black Plastic Lever with an adjuster Screw and Spring, Husky Dealers have been told to Lock Wire these together ? I find runs / starts better if you set lever so it has tiny amount of free play, leave un wired.).

This works for me. Bike starts good Hot / Cold , but there is a Technique as described above .

These last "run out" 2010s were "Thrown" together with what was left over ! I wouldnt be suprised if no two were the same !!!

 

[DakarSafari]

DG, Today I spoke with the shop I bought the bike from. While helpful, they referred me to the importer here. They were very helpful on the phone and the upshot is that I am sending the carb to them for them to tune according to their specs. When I get it back, we will know "a bit more".

 

[john01]

We called Hall's after the dealer I got the bike from said there was an "update" carb kit and he didn't have the parts. I remember a new carb bowl cap that was a little different, PJ, and something else. I'll get some time today to see if I can find the rest of the details. I also think since the bike starts ok cold a rich fuel situation could cause hot start issues. Mine actually starts quicker when warm/hot; usually 1 press kick.

 

[DakarSafari]

I think I am now going to de-rail my own thread....

As I am now fixated with this problem ... .... I thought I would dig around on the web and read some more generic stuff about hot-starting 4strokes in "race" situations.
On the ATM website I found a great thread discussing this, and in particular one guy who explained it in a way I like.....ie. physics/engineering but applied to racing.

Anyway, he explained the 'reason' for the typical hot start failure on a Four, then the procedure to get around it. Now for some of you this may seem trivial/stupid, but for me it was enlightening.

1. Unspent fuel leaves an over rich mixture - any playing with the throttle makes it worse (there is a 'but'* here)
2. The hot-start button aims to lean the mixture on re-start ... but in the case of some bikes this does not lean the mixture enough at INITIAL restart or the first kicks after the the engine shut-off/stall......that is.....there is just too much fuel vapour present even though the hot start button is letting a little more air in. Sooooo....
3. Open the throttle fully and keep it open*.....kick say 4 or 5 or 6 times. This opens the airway from filter to pipe and allows a huge amount of air to move through the barrel thus allowing the fuel to evaporate rapidly and be expelled. Effectively leaving the combustion chamber in a lean or 'no fuel situation.
4. Close the throttle, open the hot start and use the usual kick sequence.
5. Let engine fire and apply throttle as needed and close the hot start button.

I just tested this on the problem bike. Admittedly its not in race conditions, but it worked three times in a row. Each time, the bike fired, had minor backfires/coughs, then ran as normal. The kick-start lever did not try to rip my foot off either.

Comments?

* Opening the throttle to full DOES put one squirt of fuel in, but as the throttle is kept open, the new squirt of fuel is small relative to the amount of air available.

 

[DakarSafari]

OK - its official.

In a race, this bike is fucked.

Won't start in a 'dead engine start'

If it stalls, it won't re-fire on a trail.