[HandyRodder]

2008 CRF450R what should the TPS ohms be? the factory paint marks line up but i did take the TPS off to get the carb rebuild and now wont start...

black x yellow=.437 ohms
black x blue =4.78 ohms

[JimDirt]

Welcome to the site !!

Hopefully this helps ...

[HandyRodder]

Thanks Jim, i adjusted the TPS to read 650 Ohms... still no start
RANGE: 620~717

Have spark
Carb squirting (was rebuilt and ran before rebuild but was leaking gas and hard to start hence rebuild)
new plug (old plug looked lean)
valves .011, .010, .006, .005
fresh gas
timing is right (cam, RH crank, LH plug... all line up)
leak down @TDC i had to hold crank to keep it from turning and air was coming from case not exhaust or carb VALVES GOOD
ether wont start it in either the plug hole or carb air box and or through the carb.
Bike has 62hrs on it and stock piston @35hrs

Have compression... i think... it reads 60psi but not sure thats enough to make it go... i think so but its easy to kick. I know target is 78psi. Carb rebuilder said hard to read compression because of the decompressor....ready to torch it but i just had it shock and carb rebuild and $800 in ice tires. dedicated ice bike. it MUST be either carb, low compression, or spark is in wrong spot.

[JimDirt]

Hmmmm . OK try this ... Take a small hose (vacuum hose , gas hose etc. ) and dip it in some gas and put your thumb over the top , put it in the spark plug hole and release your thumb , put the plug back in (no need to install the tank) and spark plug boot , and try to start it (try it with the choke on , then off) , see if it attempts to start , this will either confirm or eliminate a fuel issue , you can also unplug (in another test) the TPS , as the bike will run without it hooked up , this should either confirm or exclude the TPS , but the bike should run with it hooked or unhooked and start right up

The compression sounds off a bit , it could be that you are getting blow by thru the rings ... this would drop the compression and cause hard starting , if the decompressor is acting up , it would most likely cause higher than wanted compression , so it sounds like it is working , though it could be sticking , maybe check the plunger , or pull the unit and make sure the pin is good and the shaft is not broken and that everything is free ( the owners manual should have a test for the decompressor) , when you are checking the compression are you kicking it hard like you would when you start it ?? , and are you holding the throttle wide open ?? , this is key for getting a correct reading ..

It does sound like most things are where they should be , though not everything ..... so eliminate each item ..... also it is possible that the stator could be acting up , have you tried bump starting ?? , this might give enough umph to get it to start , and that might lead you to the source of the starting issue ..... But I would go thru each item in the electrical system to eliminate it , and also , if it does start with the hose in the plug hole test I mentioned , then also check to make sure the gas cap vent is not clogged (if it is stock the hose can get mud dauber wasps in it , they build a cocoon and the tank wont vent and it causes a vapor lock , also the aftermarket ones , sometimes have a issue (mainly because of ethanol) with buildup and the checkball sticks and it won't vent ,, WD-40 or carb cleaner will free it up and just shake it till it moves freely ...... although a blocked vent usually is noticeable after you are riding and the bike starts to bog down , then you pull the vent line and the bike comes to life again or even though you mentioned the carb being rebuilt , maybe the float level is too low and not feeding the jets , as it only takes a small amount of fuel to get to the AP Pump , but it takes a higher level to allow the main and pilot jets to suck up the fuel

Basically I think if the hose does not make it start right up , then either you have a low compression issue (you heard air in the case which indicates ring blow by) , or electrical , most likely the stator ...

[HandyRodder]

Thanks for all your help Jim been reading a lot on this forum and learned many many things from some of your comments and others... i caved and left it at a dealer... it was ruining my marriage lol. will let you know the result. I didnt get a change to try some of your latest suggestions before the drop off at dealer, fingers crossed

[JimDirt]

No problem .... Hopefully they don't ream you too bad , as that may play havoc on the marriage as well

Let us know what the results they find are ...

[HandyRodder]

charged me 2 hours $295 but it ran great this weekend and started easy and as should. Blew shock again less than 3 hours... what i was told and read on another one of your posts is bike will run even without the TPS plugged in so look else where why bike wont start.
thanks again