Switching to Standard Exhausts

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delboyphx
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Switching to Standard Exhausts

#1 Post by delboyphx » Sun Apr 29, 2018 7:59 pm

I am in the process of returning my RZ350 to original parts, yes after 34 odd years its time to drop the expansion chambers, K&N filters and try and make the bike look original. I managed to find some original exhausts on Ebay, like brand new if you can believe that and looks great now they are back on.

I was expecting some kind of performance drop but there seems to be more going on as I notice that above 6,000 revs its really struggling for power. Up to 6000 as good as before and then it hits a brick wall requiring a gear change to keep accelerating. I am looking for things to check here, perhaps wishful thinking that you can just switch exhausts and that's it, but that was the hope.

Some additional technical details that might be important here. These exhausts also have the secondary air filter system that improves emissions by feeding air into the exhausts in a pipe close to the manifold. The secondary air filter resides under the engine in the lower front fairing (the three holes in the front of the cowling), this seems to be working although not 100% sure on nominal operation. I can feel air being drawn in from the tube that feeds up and sits under the tank so assume this part is working.

I am hoping someone out there has some knowledge of this and can give me some clues on what to check next. I have been thinking of blocking off the secondary air filter, does this make sense and if this is not working correctly would that explain the symptom. The other thing I am thinking is carbs need to go back to standard jets, again could that explain the big power drop just because of exhaust.

Anyways that's in advance for any help here.

evan_calgary
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Re: Switching to Standard Exhausts

#2 Post by evan_calgary » Mon Apr 30, 2018 12:22 pm

Did you just throw the pipes and airbox onto the bike as it was previously other than pods and pipes? If so you likely need to adjust the jetting. You will be flowing a lot less air now aka rich.

delboyphx
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Re: Switching to Standard Exhausts

#3 Post by delboyphx » Mon Apr 30, 2018 10:47 pm

Thanks for the response. Probably should have clarified that standard air filter added first and was running just fine. The standard exhausts were where performance drop became very noticeable.

I will try clamping the secondary air filter intake and report back.

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JonW
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Re: Switching to Standard Exhausts

#4 Post by JonW » Mon Apr 30, 2018 11:30 pm

you didnt adjust any jetting?
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delboyphx
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Re: Switching to Standard Exhausts

#5 Post by delboyphx » Tue May 01, 2018 12:19 am

No change to the jetting. My plan was to switch parts one at a time, test and move to the next change.
- Air box first, worked fine
- Exhausts and secondary air filter next(and where I'm at). Very noticeable problem at high revs. I have been reading up on the operation of the secondary air filter (which I also purchased with the std exhausts). Sucking air in and seemingly feeding back into the manifold, can't say I fully understand the operation but seems like a well know emission improvement technique. Standard parts for this 84 RZ model.

Next step clamp/block the intack, maybe this will help.
- Standard jetting last.

Thanks for feedback.

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JonW
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Re: Switching to Standard Exhausts

#6 Post by JonW » Tue May 01, 2018 12:54 am

you can lead a horse to water... Evan and I have tried.
80 XT500 Supermoto!
81 RD350LC Resto
82 RD421LC Hybrid
82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
83 RZ350 Resto
84 RZ500 Resto
85 RZ350 F1 Resto
86 RZ350 F2 Resto
86 RZ350 F2 Hybrid

Like Watches? www.PloProf.com & www.DeskDivers.com

delboyphx
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Re: Switching to Standard Exhausts

#7 Post by delboyphx » Tue May 01, 2018 1:27 am

Yes. Thanks for the feedback and advice.

hondaror
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Re: Switching to Standard Exhausts

#8 Post by hondaror » Tue May 01, 2018 2:15 am

As noted, you have to rejet. After rejetting, you still have a problem? The pipes might be plugged up with oil, spooge, from running too rich, as all bikes were very rich from the factory. Most did not rejet. Again, you HAVE to rejet.
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thumper580
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Re: Switching to Standard Exhausts

#9 Post by thumper580 » Tue May 01, 2018 5:48 pm

Rejet back to what is on the spec page in the service manual.
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delboyphx
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Re: Switching to Standard Exhausts

#10 Post by delboyphx » Tue May 01, 2018 6:02 pm

Thanks for advice to use standard jetting. This is next on my list. Will report back once complete.

evan_calgary
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Re: Switching to Standard Exhausts

#11 Post by evan_calgary » Wed May 02, 2018 3:02 pm

Would also help to know where you are located. Pipes and filters run a lot more air through there. Likely too rich everywhere. I usually start stock on pilots and one leaner on mains due to our elevation. Jetting changes should make significant difference and if you are working with the F1 generation bike are easy enough to do...

delboyphx
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Re: Switching to Standard Exhausts

#12 Post by delboyphx » Wed May 02, 2018 3:17 pm

Located in Phoenix, AZ. Lower elevation desert.
Any jet recommendations welcome. Thanks.

evan_calgary
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Re: Switching to Standard Exhausts

#13 Post by evan_calgary » Wed May 02, 2018 3:26 pm

In that case start it at the stock jetting and go from there. I suspect you have larger than standard jets right now. You will know quickly if you are getting closer as should run better. Jetting is a PITA as it is a dirty and ithgt job but needs to be done especially if way out like sounds your case is.

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T.RexRacing
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Re: Switching to Standard Exhausts

#14 Post by T.RexRacing » Wed May 02, 2018 8:31 pm

You guy gotta remember if he's got US spec exhaust it's a catalyst pipe and jetting requirements are totally different than Euro or Canadian spec bikes. Lemme dig in my manual out in the garage for OEM numbers and I'll post up the results.
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delboyphx
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Re: Switching to Standard Exhausts

#15 Post by delboyphx » Wed May 02, 2018 11:16 pm

Thanks guys. I have the service manual for this model. Need to purchase and switch old jets out.
Thanks again

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