Couple more questions

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Juicebox
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Couple more questions

#1 Post by Juicebox » Wed May 29, 2013 2:24 am

Ok, I got the engine started today and I have a few new questions. I sucked on the line from the oil tank to the oil pump, and when it came out the end, I put it on the pump. I had a 1/2 gallon of 32/1 permix in the tank and ran the engine until oil came out the ends of the the lines going to the carbs, and then I put them on the carbs. One of my questions is: Do I need to bleed the oil pump, or is what I have already done good enough? I dont have clear lines and cannot see the oil or any air bubbles, so I was wondering how to proceed. I will do the output test tomorrow, so I will know then if the output is ok, but I was wondering about air bubbles in the lines to the carbs.

Also, the bike doesnt seem to run that great at idle and just off idle. When I turn the idle adjust screw in on the carb, it doesnt seem to raise the idle until I screw it way in...then the idle goes real high all of a sudden. I also started with the air screws at 1 turn out. When I started moving the screw on the left carb (because it's the easiest to get to) I got it all the way closed, as in fully seated, and the left cylinder kept running like nothing had changed. I only went in with the screw, not out, and I only did this on the left cylinder, but again, it didn't seem to make a difference to the way that cylinder ran. My pilots are currently at 20, and I was wondering if that means go up in pilot size? The bike doesnt idle better with the choke out, in fact if the choke isnt shut off right away, the bike dies. I should also say that the left cylinder was popping much louder than the right cylinder. But the right cylinder also has 20 pilots in it as well, so i'm not sure that means much, but the left was definitely louder and popping more than the right.

I have done a lot of work on the bike over the last couple of years, and jetting the carbs properly is something I have put off until now. I thought about taking it in and having it tuned, but I felt like that would be taking the easy way out, and I am determined to jet my bike myself and know that satisfaction. I am sure there will be more questions on this subject in the future. Not about what jets to use, but what techniques to use to figure that out myself. Thanks everyone.

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pushstartrearset
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Re: Couple more questions

#2 Post by pushstartrearset » Wed May 29, 2013 2:33 am

i remember reading in the manual you want to bleed the pump also...just make sure you get rid of any air bubbles that may be trapped. I know w/ my daytona, one side popping louder than the other is a sure sign that one of the carb slides is higher than the other...i forget which one. In short, i take the carbs off and raise to WFO and see if they clear the top equally if not (looking straight at it...a quicky carb synch if you will), i turn the screw knob at the bell end of the carbs a bit at a time and recheck and repeat until they are perfect (short of a proper vacuum synch).

You need to list your bike details in your signature like i do...look at the bottom of my post and you'll see what I mean. Helps the others help you.

good luck.
1984 RZ350L (U.S.) Old Toomeys, oil injected!, Y-boot K&N. loctite throttle cable holder on left carb!! , 410 mains, Dynojet needles 2.0 clip, #20 pilot @ 1.5 turn a.s., 240/512 p.v.

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steveloomis
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Re: Couple more questions

#3 Post by steveloomis » Wed May 29, 2013 2:42 am

There is a bleed screw on the side of the pump. Probably best to check for bubbles there too as that would affect your test. When you do the test, capture some output in another container to make certain it is fully bled.

Have you fully cleaned your carbs? I know I've mentioned this quite a bit and don't wish to insult anyone but it bears mentioning again for clarity.

Something is wrong if one side is running better than the other. Verify float height on both. You can do it on the bike using the overflow tube along side the carb.

I just went thru a very difficult time getting my right side running without dropping out from over rich. maybe you read it, but I'll repeat.

I took my right carb completely apart and did the chem dip in a bucket then ran wires thru every passage I could to verify no blockage then blew carb cleaner thru every orfice, especially from the outside air vent to the float chamber, then blocking that hole and observing the vent hole where the emulsion tube was removed from.

What I discovered upon close inspection that someone prior had tried to seal the brass plug from the pilot jet feed as it was leaking additonal fuel bypassing the pilot jet. The sealant was coming loose. I resealed it with a bit of Caswell tank epoxy as it is gas proof. Today the bike ran better than it has since I got it running the other day.

This just proves that anything can happen to these old machines.
'81 RD350LC hybrid w/84 RZ engine. Zeel, Old style Toomeys, Yboot and filter 420 main 22.5 pilot, Air screw 2.5 turns out, DJ needle 2nd from top, Canadian VM26 carbs.
'85 KR/RZ US. Tank is seeping causing a blister in paint.....

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pushstartrearset
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Re: Couple more questions

#4 Post by pushstartrearset » Wed May 29, 2013 2:46 am

hey steve, can you take a picture of what you are talking about w/ the pilot jet feed? is this at the bell end?
1984 RZ350L (U.S.) Old Toomeys, oil injected!, Y-boot K&N. loctite throttle cable holder on left carb!! , 410 mains, Dynojet needles 2.0 clip, #20 pilot @ 1.5 turn a.s., 240/512 p.v.

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aaronmvrider
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Re: Couple more questions

#5 Post by aaronmvrider » Wed May 29, 2013 2:49 am

yes bleed pump.... if any air in pump now it will be pushed into the lines

back off your throtte cable adjusters then adjust idle... perhaps they are too tight and not allowing the slides to bottom out

get some clear lines... you will never go back to anything else

get a spray bottle with soapy water and spray on all joins to see if it is sucking air... eg water in will affect the engine idle etc... old school approach but hey it works

put up your parts list and current settings in your signature spot

i think up 1 on pilot would be a safe bet
1 x 4mm stroker rz 375cc 1983
1 x 7mm stroker rz 443cc 1984 (under construction)
1 x rz 500
1 x mv agusta 1000

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steveloomis
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Re: Couple more questions

#6 Post by steveloomis » Wed May 29, 2013 2:54 am

NO, it is inside the float chamber just above where the pilot jet screws in. There are 2 brass plugs, one for each drilling that feeds the pilot jet so this is actually downstream from the pilot jet and bypasses it. It is at the top of the float bowl but with fuel swishing around I am certain it can get sucked in. As small as the pilot jet is, any leakage at all is significant. My right plug cleaned up, well it is a new one but previously a new plug would get black very quickly. Now it is brown.

I have spare carbs and can take a pic if you need it but hopefully I described it well enough
'81 RD350LC hybrid w/84 RZ engine. Zeel, Old style Toomeys, Yboot and filter 420 main 22.5 pilot, Air screw 2.5 turns out, DJ needle 2nd from top, Canadian VM26 carbs.
'85 KR/RZ US. Tank is seeping causing a blister in paint.....

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dave_356
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Re: Couple more questions

#7 Post by dave_356 » Wed May 29, 2013 5:07 am

if screwing in idle screw does nothing then does something, it probably wasnt contacting the slide at the beginning. either it wasnt gapped correctly to start with and/or there is negative slack in the cable.
steveloomis wrote:verify float height on both. You can do it on the bike using the overflow tube along side the carb.
^this

if float level is not the same in each bowl then you will never get fueling sync'd

iirc my procedure for VM26 carb setup is basically

1. assemble carbs off bike
2. set idle gap by sliding a 2mm split pin down the venturis and adjusting idle screws- you have to do this to get both slides idle height synched. future adjustments in idle ensure you adjust both screws by equal amounts (i use a straightened out split pin cos its rounded on one side, so it will sit flat inside the bottom of the rounded venturi).
3. set air screws 1 turn out is fine, or half turn.
4. hook up a bottle of fuel to the carbs so the float bowls fill
5. no naked flames
6. measure fuel level using overflow clear tube method with carbs LEVELLED (alternatively make two measurements one each side of the carb being tested and average the measurements ie: if carbs are on the bike and its not perfectly level)
7. reset float height based on clear tube measurements
8. fuel level should be ~1mm below the gasket and exactly the same in each carb
9. install carbs attach fuel lines and throttle cables ect but dont put on the airbox boots
10. open throttle
11. jam cable ties down each venturi so the ends are sticking out where the air box boots would be
12. close throttle so the slides clamp the cable ties
13. slowly open throttle observing cable ties to see which one moves first
14. adjust throttle cables so both slides move at same time eg: the cable ties move at same time
15. remove the cables ties and install the boots
16. use removed cable ties to tie the 3 into 1 cable splitter into place so it cannot move (which would screw your sync up)
17. fire up the bike
18. fine tune idle by screwing both idle screws the same amount

you can fiddle with the air screws if you want but i dont think it makes much difference. funny thing i can remember all that without even thinking about it cos in the early days i spent so much time frigging with the carbs. i havent touched my base carb setup (apart from needle height and main jet) for two engine builds now. it just runs and plugs colour identically.

i think the real secret is using clear hose method to get fuel level exactly the same + syncing the slide pickup using the cable ties (also known as paddle pop stick method) and precisely matching the idle gaps.

the rest is just mechanics- if the jets and needles are the same, the adjusting screws set the same then the carbs are sync'd. differences will be down to damaged or worn components behaving differently.
Last edited by dave_356 on Wed May 29, 2013 10:39 pm, edited 3 times in total.

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steveloomis
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Re: Couple more questions

#8 Post by steveloomis » Wed May 29, 2013 12:32 pm

Very good step by step description. Silverstrom gave me basically the same setup advice and added to make index marks on the idle screws so you always know where they are in relation to each other and also if you have NON-US carbs that have the screw on cap, once tightening them properly, make an index mark on them as well so they are always in the exact same position. Makes perfect sense to me for on-going maintenance.
'81 RD350LC hybrid w/84 RZ engine. Zeel, Old style Toomeys, Yboot and filter 420 main 22.5 pilot, Air screw 2.5 turns out, DJ needle 2nd from top, Canadian VM26 carbs.
'85 KR/RZ US. Tank is seeping causing a blister in paint.....

Hooligan
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Re: Couple more questions

#9 Post by Hooligan » Thu May 30, 2013 1:28 am

Also, the bike doesnt seem to run that great at idle and just off idle. When I turn the idle adjust screw in on the carb, it doesnt seem to raise the idle until I screw it way in...then the idle goes real high all of a sudden. I also started with the air screws at 1 turn out. When I started moving the screw on the left carb (because it's the easiest to get to) I got it all the way closed, as in fully seated, and the left cylinder kept running like nothing had changed. I only went in with the screw, not out, and I only did this on the left cylinder,
Not being fascecious but you do realize there are two idle screws, one on each carb? You need to start out with both screws set at the identical "height" and then adjust both of them the same each time. If you only move one screw the motor will end up all buggered and won't run properly.

From all the way out, the idle screws go in quite a ways before they contact the slides. I found it really difficult to feel when the screws contacted the slides with the carbs assembled so I zero'd each screw against its slide with the top of the carbs off and the slide detached from the throttle cable. Putting a finger on the top of the slide it is easy to feel when the idle screw touches the slide.

On top of the idle screws and air screws, the carbs need to be properly synched. Welcome to the world of two-stroke carburators. :D
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

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steveloomis
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Re: Couple more questions

#10 Post by steveloomis » Thu May 30, 2013 10:48 am

Per Silverstrom, put an index mark on each throttle stop screw so you know where they are the same, this way you can keep the same relationship on each and stay sync'd. He also recommends you tighten the carb tops securely then make an index mark on them as well so you always know they are in the same position vertically and will not alter your settings. Good info...
'81 RD350LC hybrid w/84 RZ engine. Zeel, Old style Toomeys, Yboot and filter 420 main 22.5 pilot, Air screw 2.5 turns out, DJ needle 2nd from top, Canadian VM26 carbs.
'85 KR/RZ US. Tank is seeping causing a blister in paint.....

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Evans Ward
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Re: Couple more questions

#11 Post by Evans Ward » Thu May 30, 2013 11:40 am

Joshua,

Are you runnng the US spec Mikuni VM26SS carbs with all of the linkages and both the push/ pull cables? If so, I'm not sure the advice given is applicable to those carbs? Cables don't go to carb tops on the stock US assembly.
84 RZ350-Toomeys,SCR milled head, stk 26 carbs,300 M, 35 P, stock regrooved needles AS 2.5 turns out,stk air box,Banshee reeds Zeel non-progr CDI,TSRL Program YPVS,alum rad,R6 shock,GV emulators w/RT springs,fork brace,Shindy steering damper.

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Juicebox
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Re: Couple more questions

#12 Post by Juicebox » Fri May 31, 2013 2:50 am

You are right Evans...running the stock US carbs with one cable and one idle set screw. I was just reading the replies and was about to let everyone know that when I saw your post. I am not using the return cable though. I have noticed a couple of other things...one thing is that there is fuel pouring out of the bowl drain nipple (when petcock is on prime) on the same cylinder that sounds like it's popping (the left cylinder). Also there is very dark raw fuel coming out of the povervalve pulley cover...at least I think it's raw fuel...smells like it. As soon as I start the bike it starts dripping out of the pulley cover. I think thats telling me that my float isnt cutting off fuel and there is a lot of fuel going to that cylinder......right? But I wonder why the cylinder doesnt foul up and die? Would that also make that cylinder pop and sound different?

I should also let you guys know that I put a dial-a-jet kit on this bike. To mount this kit, normally you would drill a hole into the bottom of your float bowl and thread that hole for a nipple that is then connected to the dial-a-jet. But, with the stock carbs, the main jet is too close to the bottom of the float bowl and the main jet and new nipple would be too close together. So instead, I replaced the screws that close off the float bowl drains with screws that have a hole through their length, and a nipple built onto the end. I only mention this because I was worried that that screw might not be closing that bowl drain properly. But it doesnt leak when not on prime, so I dont think it is causing the drain to leak...I think my float is stuck. They also wouldnt have any affect on how its running on idle because they dont operate on the pilot circuit ever...and on the other circuits they only supplement them while the engine is under load, which this bike has not been under yet.

So...I am going to pull the carbs and check the floats. I just wrote all that other crap to see what you guys thought.

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dave_356
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Re: Couple more questions

#13 Post by dave_356 » Fri May 31, 2013 8:35 am

Juicebox wrote:You are right Evans...running the stock US carbs with one cable and one idle set screw.
oic

i have seen that arrangement on a 1988 australian rz250 before, 2x VM26 controlled off a rail much like gixxer's of similar vintage. i was wondering where those carbs came from since all other oz spec 1988 rz's ive looked at are the old school arrangement.

but anyway, they still must observe the same principles. whether the cables are split at a splitter or linked in some fashion at the rail you just need to figure out a method to ensure the slides zero (idle) position is the same and they are picked up at the same time. usually there is some kind of grub screw system that permits adjustment of these things.

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