07-07-2012, 04:25 PM #1
Very strange knocking problem.....03 gpr1300..
Just got another GPR together and this one has me on edge. Well to make a long story short traded my friend my running ultra150 for his hurt gpr. What happend was his oil pump took a dive and hurt #1 cylinder/Piston. I got the cylinder fixed and got a new piston and rings and got rid of the oil injection with the block off plate. Got my first tank of gas mixed at 36:1 and started it up with no issues other than it sounds like it has some type of a knock. I pulled the plugs and turn it over and it sounds fine with no knock! I pulled the head and nothing out of the way everything looks happy etc etc... What am i missing here? Any suggestions?
07-07-2012, 04:40 PM #2
if it sounds like this
its the nature of the beast i thought the same thing when i first built mine
07-07-2012, 06:07 PM #3
if you have wear on the intermediate splines and the drive shaft it will make a funny noise at idle.
07-07-2012, 08:32 PM #4
I dunno fellas im starting to think when my friend siezed that #1 cylinder it may have hurt the crank. I went back out and put the head back on to listen again and its knocking pretty hard. Its just weird that it only knocks when its running with the plugs in. When i turn it over with the plugs out it sounds fine.
07-07-2012, 09:06 PM #5
remove the head take that cylinder out and inspect the crank.
07-08-2012, 12:06 AM #6
Had this happen to a friend. Crank rod bearings went. You could pull the crank rod up and down 1/8th of an inch of play. On his it did do head and cylinder damage in the process. He caught it early enough that it didnt take all cylinders out with it, just two.
07-09-2012, 10:17 AM #7
Do any of you guys think if the roller bearing that slides over the wrist pin was bad it might cause a knocking sound? Or better yet i put a sbt piston back in the cylinder and it said DO NOT use the two shims that go on each side of the wrist pin. Could that be it?
07-09-2012, 02:36 PM #8
Have you double checked the piston to cylinder clearance,mine had a knocking sound and it turned out to be excessive clearance,I took the piston and cyl to machine shop to measure it since they knew what they were doin,another sign of piston slap is slight scoring in the cylinders and the piston skirts will be nicked up.I'm not familiar with the 1300, is it a nikasil cyl or a sleeved cyl,and was it bored oversized
07-09-2012, 04:26 PM #9
My cylinder walls looked perfect when i pulled the head back off...
07-09-2012, 04:33 PM #10
- Join Date
- Sep 2011
- Seattle, WA
What are the numbers from the compressions test? Also have you preformed a leak-down test?
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