Strange starting issue with DS450

[lynxmann]

Hey guys i have tried to search to see if anyone have had similar issues with their bikes but have found nothing.

Here goes: when the bike sits outside and the temprature drops the starter will not turn the engine over.
Even when sitting in my shop sometimes the starter will struggle to get going but as soon the engine starts to turn over it works normally and the engine fires right up.
I have tested and changed everything now, i put in a new startermotor and streched a cable directly from the starter to a brand new battery that is fully charged but it acts the exact same way.
To me it seems that the engine at some point in a revolution is wery hard to turn over and this makes the starter struggle sometimes when it is going to start the engine.
I have pulled the spark plugs and turned it over manually and when the camshaft is starting to press down on the intake valves it turns quite hard but there should be more resistance doing this exept it is much harder compared to the exhaust valves.
Im kind of lost here so i hope someone have some insight they can share on this problem.
Regards from Norway
Ola

[ZX11]

I am new to ATV's but I thought these big singles had a automatic decompressor to make the motor easier to turn over. Could this be intermittant? I may be way off base though.

[lynxmann]

Yes there is an automatic decompressor witch works on one of the exhaust valves but this does nothing before the engine starts to turn over.
And that is the problem to get the engine to start turning over.

But it seems like the problem occurs when the engine has stopped at a certain position and and it seems just like you have bad battery or a bad starter engine with the exeption when the engine is not cold it can get the engine to start turning over and as soon that happens it starts to crank normally.

[comander420]

maybe the decomp mechanism is "sticky" and doesn't get as sticky when warm?

[TNT]

We had a decomp stuck open once on our YAM and it would not start at all! If your description is accurate and this is a hot/cold issue then unless it’s a faulty coolant or air temp sensor or ECU bad magneto area in disguise, it almost sounds like a mechanical issue with expansion and contraction of metal gap problems but I’d doubt it.

BUDDS always helps at moments like this if you can look at any fault codes. Otherwise I’d replace the decomp, coolant temp, AAPTS( in air box make sure it's clean) sensors, but it’s hard to say. When it does not cold start do some voltage checks at the starter eliminate the electric possibility then move to fuel has to be one of them more than likely?

Seen this sort of thing on cars where something is going out but you got to wait till it does, so when it won't start troubleshoot electrical and fuel.

[lynxmann]

Hi Terry, the bike starts just fine when the starter works normally.

The problem is that when the bike sits outside when the temprature drops and you try to start the engine does not turn over at all.
If the bike is inside in my warm shop it starts but half the time when you try the starter struggles to get the engine cranking.

When the engine is warmed up everything seems to work just fine.

I belive there is some issue in the engine but where to start looking i have no idea.

[TNT]

Well with all that happening we boil it down to temp related thats for sure.

Coolant or air temp sensors problem would be over the rpm range ECU same.....A starter or mag winding doubt it. Yeah it's something mechanical in the motor is my guess too.

Place to start would be the aluminum engine components, depending on the alloy and finish they can have a thermal expansion ratio and wear twice that of steel. I'll chew on it for a while and ask our engine builder what gap could cause his. I'm more inclined to think something wore out rather than expanded out of round because the spring back on both is good, ....tricky one! :confused: If you have not been through the motor and rebuilt it in a while this may good time to gap and wear check everything.

Maybe you should check your valve clearances pull the head and check all the gaps like your cam bearing's etc......

[lynxmann]

Yes seems like that is the only way to go from here, just wanted to check that if anyone was having similar problems and could point me in the right direction.

The bike only have 60 hours on it but it is a road legal bike so compared to a bike run at the track or in the woods it is being run at higher rpms over longer periods witch in my opinion this engine type is not designed for.
Kind of asking for trouble:ermm:

[X400EX]

I have same problem but it will do it at anytime (hot or cold).

I have to push on the start button quickly a second time then it cranks and starts normally.

[florentino]

check your valves are they adjusted if not any 4 stroke motor starts to have a hard time crankin. check all grounds and spray all conections with electronic spray.

[LTRracer4]

Originally posted by lynxmann
Yes seems like that is the only way to go from here, just wanted to check that if anyone was having similar problems and could point me in the right direction.

The bike only have 60 hours on it but it is a road legal bike so compared to a bike run at the track or in the woods it is being run at higher rpms over longer periods witch in my opinion this engine type is not designed for.
Kind of asking for trouble:ermm:

You have 60 hours of road riding on the bike? Have you rebuilt it yet? If not, def. time for a new piston and maybe recut valve seats. When its down check over everything. I guess mx is a bit harder on a bike, but i can imagine roads arent easy on it either. After 60 hours definatley pick it apart.

[hotshotgoal30]

hey man just thought id let you know last year i bought my DS for christmas i had the same problem. if it sat in the garage it was fine. as soon as i rode it in the snow and it was ouside in the cold it all of a sudden wouldnt start. had me thinking for awhile, mind you it as brand new. come to find out my battery had a "dead cell" my machine sat on the showroom floor and the battery went dead. hen i bought it they recharged it and it was fine. till it got cold. i took it in and they gave me a new battery under warranty. never had another problem again. so it sounds to me like you have the same problem. id go with a new battery. you never know how long these things sit on the showroom floor

[TNT]

I remember that with you but he said he had a new batt in his first post. :D

[hotshotgoal30]

ha ha gues i should read more carefully. lol just trying to help. lol sounded like my problem

[400exc]

I know this is an old thread but I had this strange problem too. Took it to my dealer and they tested it and a plug by the ECU on the wiring harness was junk. When I went to start it, it would just click and not turn over. When the engine was warm it would start, but like what you guys said, when it was in the cold it wouldnt start.