To much compression for battery

[maska]

I am looking at an "04" YFZ450 with a Big Bore kit w/ high comp piston, exhaust, hot cams. All the work was done legit at the dealership. The seller claims the machine needs to be jumped off a car battery to start because there is too much compression for the stock battery.
If any one has any insight as to if this if a comon problem or a story please let me know.

[Ride1Rob]

When I had my high comp piston I had that problem as well. Had to upgrade to a R1 motorcycle battery. Some say they still run their hc pistons off of the stock battery. Seems like it's probably hit and miss with each bike.

[yamahaman623]

my buddy had to put a cbr battery in his 2005 yfz and his compression was only 13:1. it still was wierd when you started it compared to my stock one. but some people put a kick start on it instead

[younggun95]

Definetly need to put in the bigger battery. Essential with a bigger motor, and a good upgrade even with a stock motor.

[GWTT]

BS! I have 13.5:1 Cp piston. porting yadda yadda and I consistantly start it with a stock battery for a yfz. didnt get it from yamaha (golden west cycle) but its ment for a YFZ. the battery probably has a bad cell in it or a stator not charging. the YFz's have always had charging problems even the aftermarket stuff like ricky stator have issues. sound like the big bore has too much clearance in the rings, needs some valve shim adjusting, carb cleaning or cam timing issues.

[florentino]

are you puting race gas.. ??? it runs cooler.. its the valves the need to check .. also you need a batt tender.. batts dont last more then 1 year on hi comp motors ... stock batt is fine. how can you put a r1 batt in there ??

[Ride1Rob]

Originally posted by florentino
how can you put a r1 batt in there ??

It mount directly up just like the stock battery. Is alil bigger so the plastic has to be cut a little.

My bike had the same problem and all of my valves were in spec. I had just put the motor back together and the stock battery simply didn't have enough juice. I sold the stock battery on ebay (guy that bought it had no problems) and got the R1 battery (and I no longer had any problems).

[91gtig60]

sounds like they got the cam chain tennsioner adjusted too tight, i have seen this be a problem

[Ride1Rob]

How do you adjust the cam chain tensioner too tight? There's an internal rod that goes to a certain length when released. When it gets worn it'll cause too much slack in the chain.

[91gtig60]

you let it wind out automatic, but you can give it anotherturn or 2 and make it too tight. i have had one so tight that the engine wont crank untill i reset itto the right tennsion
Originally posted by 91gtig60
sounds like they got the cam chain tennsioner adjusted too tight, i have seen this be a problem

[mitch-#4yfz]

put a bigger decompression pin on the exhaust cam. hot cam will do it for for free if you send it to them

[maska]

I took a chance and got a stock battery to try and avoid cutting **** up. It seems to be running fine. But I am yet to really take it out for a beating.
SIDE NOTE: I don't miss the Raptor. The YFZ F*%KIN hauls ***. Thanks to the guys on the other posting I had deliberating between YFZ or Raptor 700.

[Ride1Rob]

Originally posted by 91gtig60
you let it wind out automatic, but you can give it anotherturn or 2 and make it too tight. i have had one so tight that the engine wont crank untill i reset itto the right tennsion

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