no power after 3rd gear

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troublintx
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no power after 3rd gear

#1 Post by troublintx » Sat Oct 08, 2016 2:31 pm

Hey 2 stroke gurus, I bought a 1985 RZ 500 out of the Houston Texas area that many of you are familiar with this bike.
anyway i brought it home went through all the systems flushed radiator, flushed fuel lines, cleaned and filled the 2 stroke oil tank. and rebuilt the carbs,installed new plugs and fired her up. Ok this is where my problems start, I can hit red line in bottom three gears but as soon as i hit fourth i cant get past 8 grand it starts to bog down. I was thinking kinked fuel line or clogged pick up in tank seeing how i didn't mess with the tank im thinking that is where my problem is. Anybody else ever had this happen to them?

silverstrom
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Re: no power after 3rd gear

#2 Post by silverstrom » Sat Oct 08, 2016 3:19 pm

That bike sat for 14 years. Did you rebuild the motor, or at least pressure test it? If you didn't pressure test it you should stop riding now and do so because your symptoms accurately describe a leaking crank seal. A lean mixture limiting RPM and power. The end result will be very expensive if it is ignored.

gpaddict
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Re: no power after 3rd gear

#3 Post by gpaddict » Sat Oct 08, 2016 7:42 pm

Probably not crank seals, if you can run out in the first three gears. Also, if crank seals are that bad, it would be a bitch to get it to start with the kickstarter.

silverstrom
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Re: no power after 3rd gear

#4 Post by silverstrom » Sat Oct 08, 2016 7:58 pm

I missed the bit about redline. Oops.

Check your cylinder compression. Bet you'll see some interesting numbers.

troublintx
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Re: no power after 3rd gear

#5 Post by troublintx » Sat Oct 08, 2016 8:47 pm

i just cruised out slow in the bottom three and nailed it in 4-5 and got up on the pipe but ran out of road!!!
guy cruised up behind me on an R6 as i nailed it and was very surprised when the back tire broke loose and i pulled away!!

i am going to drain the tank and pull the pick up out Im sure is caked with varnish, I will post my findings.

And Thanks Guys I appreciate and respect your input into my situation!!!

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two-stroke-brit
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Re: no power after 3rd gear

#6 Post by two-stroke-brit » Sun Oct 09, 2016 7:41 pm

watching with interest.
mark
She might not be pretty but always a fun ride !!

troublintx
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Re: no power after 3rd gear

#7 Post by troublintx » Sun Oct 09, 2016 10:15 pm

removed the screen from the tank and it was spottless, so im back to square one. any suggestions would be greatly appreciated

silverstrom
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Re: no power after 3rd gear

#8 Post by silverstrom » Sun Oct 09, 2016 10:47 pm

Start with the suggestions you already have. You should be concerned with leaking seals and low compression.

You still haven't said what you did to the bike. It sat 14 years in storage. Then what?
Last edited by silverstrom on Sun Oct 09, 2016 10:54 pm, edited 1 time in total.

troublintx
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Re: no power after 3rd gear

#9 Post by troublintx » Sun Oct 09, 2016 10:51 pm

Silverstrom what are you expecting me to find?

silverstrom
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Re: no power after 3rd gear

#10 Post by silverstrom » Sun Oct 09, 2016 11:07 pm

Did you do anything to the bike when you got it after 14 years of storage?

troublintx
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Re: no power after 3rd gear

#11 Post by troublintx » Sun Oct 09, 2016 11:20 pm

Yes I posted all that i did!

Im not sure how to test the cases, I will do a compression test tomorrow and post the numbers.

troublintx
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Re: no power after 3rd gear

#12 Post by troublintx » Sun Oct 09, 2016 11:29 pm

silverstrom wrote:Start with the suggestions you already have. You should be concerned with leaking seals and low compression.

You still haven't said what you did to the bike. It sat 14 years in storage. Then what?
I have done nothing to the motor other than change the oil. I dont pretend to know everything about 2 stroke motors but it seems to me that if im getting to redline in the bottom 3 gears i dont understand where a crank seal can pick and choose which gears it will hold in? Educate me Please!!!

silverstrom
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Re: no power after 3rd gear

#13 Post by silverstrom » Sun Oct 09, 2016 11:38 pm

If all you did was change the coolant and fuel lines and clean the carbs you haven't done nearly enough to be riding the bike.

2 strokes don't like storage. Crank seals dry out and crack quite quickly. Any bike that has been in storage for any length of time needs to have the cases pressure tested. That will check crank seals, base gaskets, head gaskets, powervalve seals, etc. The ONLY WAY to test crank seals to pressure test and vacuum test the cases.

You didn't do a compression test so it's possible that compression is very low. Rings will stick while in storage. Cylinders will corrode while in storage. Do a compression test. Look for around 120 PSI in each cylinder. 110 in all 4 would be acceptable. less than 100 and you have a problem.

Until you have that information, which should always be the starting point with any bike out of storage, you can't move forward. You need to start at the beginning, especially with a bike you know nothing about.

Typically to test the cases you need to block the exhaust ports and add air through the intake. Test the lower cylinders as a pair and test the upper cylinders as a pair. You want the cases to hold 5 PSI for 5 minutes. Do some searching on this site and Google and you'll find what you need.

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two-stroke-brit
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Re: no power after 3rd gear

#14 Post by two-stroke-brit » Sun Oct 09, 2016 11:46 pm

I had a gt750 that behaved the same , if I nailed it it would rev to the red line in the low gears but
Would fade as the ask got harder. It was bad crank seal.
A leak down test will reveal if the seals are good or suspect .
She might not be pretty but always a fun ride !!

silverstrom
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Re: no power after 3rd gear

#15 Post by silverstrom » Sun Oct 09, 2016 11:51 pm

As load increases it will become harder to hit redline with a leaking crank seal. Easy in lower gears.

I'm not saying you absolutely have a bad crank seal. I'm saying that after 14 years in storage it is very likely that you have leaks. If you don't, yours would be the first. Riding the bike without proper testing is risky. It will quickly get very expensive if and when it does go wrong. Keep in mind that the best performance is on the ragged edge of lean. A leaking right side seal may not be obvious as it will suck in gearbox oil and hide any evidence of running lean.

Low compression will limit your performance, obviously.

Anyway, my point was that you shouldn't be riding a new to you bike that has been in storage for 14 years with first making certain it is fit to ride, and that goes well beyond coolant and adding oil.

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