Springs vibrate

[jboomer]

The springs on my pipe just barely touch the head of the pipe and cause a very noisy vibration. What do you guys recommend to stop this? I was thinking wrap something around them, but what could withstand the heat?

 

[marcusgunby]

Some heatshrink tubing?

 

[Studboy]

Also if you put a little silicone RTV inbetween the spring coils it lessons vibration and fatigue.

 

[Rcannon]

I wrapped my spring in clear vinyl tubing before I installed them. I think the size was CV-6. 3/8" inside diameter. It worked very well and is not bothered by the heat.

 

[Lorin]

Black fuel line from the local auto store. Cheap and heat resistant.

 

[Jaybird]

I like studboy's suggestion.

 

[jboomer]

The bike shop suggested some type of clear silicone high temp tubing, but didn't have any suggestions except to go to an auto parts store. Advance Auto Parts guy said he had no idea but to go to a high performance car shop. The AAP guy said that fuel line would melt and heat shrink tubing is only rated to 350 degrees. The high performance car shop wants 30 bucks for a roll of heat resistant tape, with no guarantee that it would make any less noise than the spring itself. I bought the hightemp RTV gasket maker and have filled the springs with it and built a "layer" around it. Once it dries, hopefully that will do it.

Any idea how hot that head pipe gets? The RTV is rated up to 675, the heat shrink only 350.

 

[marcusgunby]

Heat shrink will eventually burn through, but it only takes a few minutes to put some more on.

 

[Rcannon]

I dont think the area your talking about gets hot enough to worry so much about. The clear vinyl tubing I used (1.00 per ft.) at Home depot is holding up well enough I am not looking for anything different. I will probably try studboys suggestion next time.

If he keeps coming up with this stuff, how about we promote him to "Stud Man"?????

 

[jboomer]

Well, I bought 2 inches of the black 5/8 fuel hose and put an inch on each spring. I rode the bike down the street (run time maybe 10 minutes) and back and they have melted through. So, that didn't work. But, the vibration was still there. If I put my foot on the pipe and rev the engine, the vibration goes away, so I know it's the pipe. Could it be where the pipe fits into the cylinder? The rubber Orings seemed very inadequate for the job they hold. The gasket is nothing more than a copper "washer" so it doesn't help much. Has anyone tried the high temp RTV silicone around this part of their pipe? That will probably be my next move. Just lather it around the pipe inbetween the Oring grooves and also a thick bead around the front where it meets the cylinder at the copper gasket. Sound good?

 

[Rcannon]

The pipe o rings can make a difference. One other thought might be to check all the mounting brackets for the pipe. Are the springs still ok? I would imagine they could stretch and not give good pressure after a while.

 

[jboomer]

The springs are good, but like I said about the Orings, not real impressive! They slip into their little groove and just barely rise above the surrounding pipe. They were like this new too. The mounting brackets are good too. I'm almost convinced it's this head to cylinder junction that's causing all of the noise. What do you think about the RTV idea? Any drawbacks to that?

 

[marcusgunby]

The or ings make a big difference-a quick fix is to wrap plumbers tape(ptfe) around them-it holds up well to the heat and i have actually used it without o rings when in a fix.

 

[Studboy]

Good idea Marcus. I didn't know that PTFE would hold up to that heat, interesting. jboomer, I coat all of my exhaust connection with Permatex Ultra-Copper and it holds up very well. It will last you at least half a year, maybe even more. Make sure that the surfaces are clean before you apply though, or else it will just slip off.

 

[marcusgunby]

The time i found this out was at a dyno session-i wanted to try a different pipe-i used cheap o rings from work-normally i keep loads and fit new ones each time i remove the pipe-well i forgot my spare ones-took the pipe off and the or ings fell in bits.It takes me a hour to drive to the dyno and i wasnt going to go home-so i wrapped PTFE tape around the junction-it worked perfect and i left that pipe on for a good few weeks like that.Now if i remove the pipe and the o rings are shot and i have no spares, i do the tape trick.

 

[UKcr125rider]

R we talking about the same PTFE tape that you wrap around threaded water pipe joints? The white flimsy stuff? I've used high temp gasket sealer when i was stuck once. Worked well intil i got the right parts.

 

[marcusgunby]

Yep thats the stuff-cost less than a pound -lasts for ages and you can use it on your clutch lever and brake lever mounts, so they spin if you crash-real handy stuff.

 

[bigred455]

Originally posted by jboomer
The springs are good, but like I said about the Orings, not real impressive! They slip into their little groove and just barely rise above the surrounding pipe. They were like this new too. The mounting brackets are good too. I'm almost convinced it's this head to cylinder junction that's causing all of the noise. What do you think about the RTV idea? Any drawbacks to that?

.....

J boomer Go to a pep boy's and get o- rings for the exhaust pipe they are called o-TITE THE WIDTH is 1/8" I.D. 2' od 2-1/4 they cost 1.50 for 4 of them,oem is 6.00 for 2. They are thicker than oem and give a nice fit when in the cylinder.This size works great for the kx 250 pipe been using them since 98 I guarantee you it will not leak at the junction.Just put a little grease around them before pushing the pipe in, it is really a nice tight fit.Another thing which is causing the rattle is the copper gasket, they thin out really quick Either go buy a new one or use 2 old ones together.Do yourself a favor don't even buy the fmf pipe springs they are junk use the oem. SEE YA.

 

[jboomer]

That's awesome with the orings bigred! I appreciate it! Thanks to everyone for the ideas!

 

[Studboy]

The FMF springs are junk. I bought a pair and one broke within the first three rides, brand new.

 

[Sawblade]

jboomer,
My 97 YZ 250 had considerable time on it and the springs started to make all kinds of noise. I replaced them and solved the problem.