[twatwaffle]

So I installed a new TRX450 piston, had the cylinder honed, and had new Kibblewhite valves etc. installed. Threw it all together over the past week or so. Got it all buttoned up today and tried starting the bike. The starter cranks halfway, then stops. I've tried it a few times, same deal. Got a big backfire once.

I'm not sure what this is indicative of. I'm certain I threw everything back together properly; I followed the service manual for reassembly and everything.

Video to assist with my crappy explanation:

https://vid.me/i5my

[JimDirt]

sounds like the de-compressor is not working and/or the timing is off , did you try kick starting to see if it would actually start/run ?

The backfire is indicative of timing being off , so i would make sure your 3 sets of marks line up ,(1) the left small round plug mark ,(2) the 2 lines on the cam gear should be flush with the head(level) and line up with the arrow towards the front , (3) and the clutch side round plug for the Balancer Shaft should all be lined up exactly

[twatwaffle]

Tried kicking it once or twice then I had to jet for work. I'll try it again in the morning.

I was pretty sure I had the timing dead on; I had the cam gear off for the rebuild, put it back on with the lobes facing back, divot lines lined up with the arrow, and the dot in the right side window lined up with the arrow. I realize now that I should be using the flywheel notches for better accuracy, so there's a possibility I'm off by a tooth on the camchain. I'll take it apart tomorrow to confirm the timing is correct.

That being said, it doesn't really explain why the starter isn't turning the engine over and stops after half a second of cranking. I didn't have any issues kicking it over so it doesn't seem like the compression is excessively high, indicating advanced timing (I would imagine) so I'm not sure what's going on with that.

[JimDirt]

If its a high compression piston (13.5-1) , then if the De-Compressor gap is not exactly right , the starter will hardly be able to turn the motor over

[twatwaffle]

Alright, I still can't figure this out.

I went out this morning and kicked over the bike; started on the second kick. Didn't feel like there was excessive compression and it was relatively easy to kick over (mind you, I'm used to kicking an XR650R and I probably couldn't tell a difference in compression). It seemed to run ok; I've just installed an R&D flexjet screw and haven't set it up right so it wasn't idling off of choke, but otherwise good. A few more kickovers and it was running well, just not holding idle.

I tried to use the button to start it, but had the same problem. Bike wouldn't turn over, barely cranked once but similar issues to the previous video. Like the battery was dead or there was too much compression.

I took the whore apart again; checked the timing off the flywheel, lined it up with the cam gear marks and the arrows, same with the right side window on the balancer. Everything was good; clearances on the intake, exhaust and decompressor are all well within spec. With the spark plug out, the bike cranks fine with the e-start. Once the plug is in, it struggles. Again, I'm thinking/guessing too much compression...?

The top end was rebuilt with a new, OEM TRX450R piston and rings and new OEM base and top gaskets; everything OEM and as recommended here and on other forums. New oil, plug, Kibblewhite valves/retainers/guides and the OEM head valve seats were cut and resurfaced, OEM cylinder was honed. I assembled everything per the service manual. Only real screw-up was almost stripping the rear valve cover bolt hole...but it seems ok.

Any ideas? I tried messing with the decomp clearance - loosening it and tightening it and trying the e-start, but there didn't seem to be much of a difference. It was in spec; .28mm for the right exhaust valve and .35mm for the decompressor arm with both feelers in at the same time.

[twatwaffle]

Here's a vid with the spark plug in:

https://vid.me/6arq


And spark plug out:

https://vid.me/rG6L

[twatwaffle]

So...I'm a bit of an idiot. I put too much faith in the non-OEM battery in the bike. I'd had it on the trickle charger a few months ago and had it topped up. In a last-ditch effort, I put it on the charger this afternoon and gave it a few hours. Went to hit the e-start and it cranked over like a mofo, with the plug in. Sometimes the simplest solutions are the best solutions.

Might be in the market for a new battery shortly. Thanks for the suggestions though, guys.

[JimDirt]

Wow ..... well . i will recommend a Shorai , i have one in my 450X and its been in there since 2011 , my bike has been sitting for a month , and it started right up

[woodchuck]

OP- Glad to hear you got her going! Simple is good!

Jim- Do you ever use a custom charger on that Shorai? Or does it maintain all by itself over those years?

[JimDirt]

woodchuck:
I normally just let it sit , even over the winter it usually starts right up in spring , i have had the Shorai since early 2011 , its the LFX09L2-BS12 , its the 9 amp one (135 cca) , not the 12 amp , so its the smaller one of the 2 that fit the X's (LFX12 is the larger one , same basic physical size , just more capacity and about $50 more), i do have a Interstate 5 Stage Automatic Charger (Model# 12V1500)(its about the size of a Shorai) , if it ever does go down i use it , you do not want to "quick charge" a Shorai , LI batteries don't like that and they won't last , the charger i have cycles batteries slowly and then "floats" them , so i use it to keep my Motorhome battery up when its sitting , and on the rare occasion i run my X battery down , its what i use , so far 4 years and counting on the Shorai , they do make a Shorai specific charger that's made for those type of batteries , i just have never had the need to get one , since mine has only gone down 2 times that i can remember in the time i have had it , and both were because i was constantly cranking on the bike , searching for a electrical issue (the power wire came off the coil while removing the tank on my X and it took me a while to figure it out , since it still "looked" attached , but it was not getting contact)


And a kind word to the OP , this is a family friendly site , so careful on the words used here , the owner (Ken) is very adamant about this , in order to keep the site "family friendly" , its one thing i like about this site , its not chaotic like some "other" forums are that i used to go to , the user name is sketchy enough , so just use a little discretion on the language and all is good , if the word is G rated , then it will usually suffice for a explanation .... otherwise , glad the battery was the issue , and no , a cheap battery will not crank these bikes over very well , i even have to use a "good" battery on my Utility ATV , it does not like Wal-Mart batteries at all and will not even crank over with one (pretty much like your symptoms)