Gozer's RZ250R

[g0zer]

well done , why did u wanna copy naths "legend status" bike tho

hehe ripping on peoples bikes is bad karma ritza, you are old enough to know that!

you will be happy to know i used velco instead of gaffa tape to attach the GPS

[rgvlee]

why not fit up the rgv speedo and drive?

[g0zer]

why not fit up the rgv speedo and drive?

i might do so in the future. i have fitted the speedo gearbox, which is required as an axle spacer for fitment of the front wheel. i did briefly look for an RGV speedo cable at 2 wheel wreckers.

for the time being GPS does the job, it gives me a speed reading and trip computer.

[Nath]

For the price you'll pay for RGV clocks why don't you get yourself a nice digital one and fuck off all that mechanical shite..

[TurboR1]

Lee can help with installation.

[g0zer]

ive figured out how to sync the carbs

there are little windows in each carb, when you open throttle to 100% each window shows a marker- adjust cables till markers are exactly the same in the windows (with motor off).

then adjust the butterfly stop screws till 0% throttle holds open exactly the same. i did this by ear (with motor off)- wound them both out (so the butterflies were closed to the max at 0% throttle) then wound one carb in slowly while actuating throttle until i could hear them clonking closed separately. then adjusted them so they were the same and slightly ajar.

then wound in both pilot air screws then opened them 1.5 turns.

then tried to start the bike- idle was only 600RPM.

Increased idle to 1200RPM by screwing in the butterfly screws equal amount for each carb.

Fiddled with pilot air screws till RPM peaked (motor running) by adjusting them equal amounts, then screwed in 1/4 turn to make slightly rich.

readjusted idle with butterfly screws.

i can now sit in 6th at 100kmh without losing speed for the first time. I might play with them some more.

edit: i then almost ran out of oil and fuel near the windsor and had to roll it into the fuel station and buy some outboard 2 stroke oil :p

[ritza]

you,ve been peeping at the manual again

[g0zer]

you,ve been peeping at the manual again

hehe manuals are useful! i used to tune my torana which had a 350 holley using much the same method, just there was only one of those.

i think i can get the bike crisper, while i was sitting in my garage for a little while when tuning it, blipping just felt really strong and crisp. then i continued to tune and it went away again.

on the holley you could tune -50RPM lean or -50RPM rich, it was much more sensitive.

On the RZ dual carb setup you only seem to be able to tune rich- screwing out the pilot air screws increases RPM to a point.. if you keep opening them up RPM doesnt seem to fall back down which seems wierd to me.. too lean a tune should cause the motor to run poorly same as too rich eh?

[sathid]

I'm pretty sure that the general consensus is that the windows are not very good for adjusting the carbs. check out the "lolly stick" method on the rz forum.



Too lean will cause the rpm to rise rapidly mate. Often sure sign of an air leak.

[g0zer]

I'm pretty sure that the general consensus is that the windows are not very good for adjusting the carbs. check out the "lolly stick" method on the rz forum.



Too lean will cause the rpm to rise rapidly mate. Often sure sign of an air leak.

thanks for the tip sathid, i will check it out.

Boing !! Yearly repost.....

Following 4 requests .......

Balancing two-stroke twin carburettors.

This method has been used by myself since 1981 on all of my RD350 LC Yamahas and also on air-cooled RD Yamahas and the odd Suzuki X5 / X7. It helps to syncronize the carbs and eliminate or reduce any mid-range flat spot.

TOOLS NEEDED;
You will need two pieces of flat wood / plastic approximately 10 centimetres in length, 5 millimetres in width and thick enough not to bend. I use old ice lollysticks, cut to size. The bike needs to be upright – NOT on a sidestand – so you will need a centrestand or paddock stand or another method of keeping the bike upright. Also an 8mm and 10 mm spanner or good adjustable.

· Remove the rubber tubes that join the carbs to the airbox, or take off any pod filters (K+N or similar)
· Slide one piece of lollystick into the rear venturi of each carb, going far enough in to just touch the back of the needles, then out a few millimetres – get the depth the same on both carbs.
· Kneeling on the right hand side of the bike (with the ignition OFF) slowly open the throttle whilst watching the lollysticks closely. You need to get the sticks in line with each other in your line of sight. You no doubt will see one stick `dip` before the other now – you`ll be surprised by how much….
· The cable on the carb that’s `dipping` its stick second should now be adjusted.
· To adjust the throttle cables you will need to loosen the adjusting nuts at the top of the carb. Initially you`ll probably turn the nut through complete 360 degrees but open and close the throttle every ½ turn too to check the amount of `dip`.
· As you get close to balancing the `dipping` of the sticks you`ll only be turning the adjusters 1 face of the nut at a time – maybe even less.
· Once the sticks dip at the same time, tighten up the locking nuts on the adjusters, and remove the lollysticks….. now open and close the throttle FULLY and rapidly in quick succession.
· Replace the sticks in the carbs and re-check for parallel `dipping` … if they need adjusting further, repeat as necessary.
· Once you are happy, remove the sticks, replace the rubber connecting tube / pod filter and start the engine …. Be careful NOT to use the throttle harshly – but turn the handlebars fully from lock to lock…. Should the revs rise when you do this, adjust the free play of the throttle cable at the twistgrip end – NOT the carb end.
· Once you are happy there is no more adjustment needed, you can then go and test the bike on the road.

Jetting an RD350LC;
Standard factory setup, using standard airbox / pipes and NO porting work, jets for RD350 LC are 190s for early models – 220s for later models – 1981 onwards.
Needle position is middle of the 5 available
Using pod filters usually damages air flow unless you have a highly tuned motor.

With ANY expansion chambers ALWAYS jet higher than you need – until you are CERTAIN that the bike is running rich, go high on jetting … its cheaper to buy 2 or 3 sets of new jets than rebuild the top end after a seizure.

Paul Love. P4LO1

Tel 07812 197967

from The Lolly Pop Stick method of balancing carbs .......

[ritza]

lolly stick is the bestest method ...are you running power jets on yours ?

[g0zer]

lolly stick is the bestest method ...are you running power jets on yours ?

umm what are those? are they good?

although i dont want to strip the carbs right now. i just want to get the bike in a reasonable state of tune so i have a bike while i slowly bring the R1 back online.

i can see the advantage of the lolly stick method, it exagerates differences in sync. I will use it as soon as i finish fixing the wheel bearings :p


http://www.50cc.nl/2stroke_pleasure.htm?rd250.htm~TsMain

jollymoto chambers



LC Racer Page, TZ350 and 250 Website



Setting up an LC Racer [Setting up an LC Racer]

Porting: Get hold of a Dremel or die grinder and carefully raise your exhaust ports by 1.5mm over stock, checking and measuring constantly. Remember, there’s no turning back if you take too much metal away. If you’re keen, polish the exhaust duct (between the bore and exhaust boss.) to help prevent carbon build up.
While you’re at it, sharpen the bridge between the two transfer entries, but don’t over-do it and also carefully trim your base gaskets to match the barrels.
Some two stroke heads even go to the extent of marking the outline of the transfer inlets on their pistons at BDC and die grind the excess piston skirt sides away to provide the maximum fuel flow into the transfers. An obvious problem here is matching piston weights. I really don’t think it’s worth the hassle to be honest.
Compression: All I ever did with my LC’s compression wise is remove the head gasket. I can’t recall the figures, but I know it did seem to provide a noticeable improvement in "seat of the pants" pull out of corners.
When using this method, you need to lap the barrels onto the head by turning them upside down and using valve grinding paste to ensure a good seal. To seal them, use plain old Selley’s Silastic. It's cheap and it works.
It pays to keep an eye on squish clearance too. Bend a short length of 2mm soldering wire at 90 degrees and thread it down through the spark plug holes so that it touches the bore. Turn the motor over by hand, squashing the wire between the piston and the head. Measure it, the thickness should never be less than 0.7 to 0.8mm.

Pistons:

The original Yamaha items are the best, though very expensive, something like $100 Aus. each or more. You can buy aftermarket pistons from a few companies which are well worth trying. Wisecos can be used, but being forged they require a larger piston/bore clearance and a lot of warm up time to be reliable. Saying that, a lot of guys fit them to TZ750’s with success, but it's best to stick to cast pistons if possible with LC's.
Some guys enlarge the transfer holes in the back of the pistons or even cut the back apron right out to increase flow/ inlet duration. This is a bit risky, obviously it can weaken the piston and lead to high wear and failures. The best thing to do is just measure the orifices and ensure that all four ( two pistons ) are identical with a little light filing.
You can leave the lower piston ring out safely as well to minimize drag on the cylinder wall.
After each race meeting , pull the top end off the bike ( a 15 minute job, I’ve timed it) and gently rub any score marks off the pistons with fine "wet and dry". Marks on the back of the piston can indicate too small a pilot jet, on the exhaust side, too small a main jet.

Exhausts. If you’re running a 250, get hold of some good race chambers like those dimensioned below. This is the single, biggest power increase you will get with these bikes. The stock exhausts are very restrictive.

Please note: 1. You'll notice the stinger section of the table is divided into two sections. Ignore this and treat it as one length.

2. The stinger length includes the muffler. For the record, the muffler body itself is 220mm long.

3. The header cone section is measured from the flat mounting face on the cylinder.

4. They are suited to a 250 LC and would best be described as "peaky" LC chambers. But saying that, being an LC, the thing was still dead easy to ride and had heaps more midrange than a TZ.

You’d be amazed how many sizes of main jet you have to go up to compensate for the improved breathing. You'll need to run approx. 340 mains in the stock 26mm carbs with the mods listed in this story.

http://www.kartpipes.com.au/ [Greg actually manufactures exhausts here in Australia so if any of you Aussie LC racers want a set of race pipes that actually work]

Carburettors. The stock 26mm Mikunis are fine for a 250LC. Maybe 28’s, but not much bigger. For a 350, 28’s or 32’s would be better.

• Powerjet carbs are worth considering due to the fact that they allow more accurate tuning and help improve top end power as well as reducing the chances of seizure.
• Flat-slides such as Lectrons are allowed, as long as they are "of the era". I personally don't believe they offer any significant advantage over round slide Mikunis.
• Running some sort of pod air filters is a real good idea as well, they extend the service life of your motor a lot.
• As far as synchronization goes, refer to the "TZ Tips" section of the website for details.

http://www.motocarrera.com/products.htm

[sathid]

IIRC power jets are small jets that open when the throttle is quite wide open. Not all of the rz models had them.

[g0zer]

i am starting to wonder about chopping open, gutting then welding back together stock RZ chambers instead of trying to source and buy aftermarket race chambers...

does anyone have any thoughts on this? will it make the bike run worse, better or no difference?

[ritza]

if you have the cigar shaped pipes, dump them and pick up the later 85 on f2 separate can type .they are a good chamber design, a lot lighter and you can chop them for even betterer choonin good link on the rd forum uk on wat to do

[g0zer]

if you have the cigar shaped pipes, dump them and pick up the later 85 on f2 separate can type .they are a good chamber design, a lot lighter and you can chop them for even betterer choonin good link on the rd forum uk on wat to do

cool thanks.

i have the F2 chambers, with some pretty nasty looking baffling inside. i was thinking it would be pretty easy to cut them open at the back cone seam, drill out all the rivets holding the internal baffling, remove baffling then weld the cone back on.

or instead of welding back together, maybe i could create a flared joint and hold the rear cone on with sealant, clips and springs? this would be good for decarbonising

[sathid]

rz on mick abbey pipes:

http://i49.photobucket.com/albums/f2.../Dugs_YPVS.jpg

[g0zer]

rz on mick abbey pipes:

http://www.perthstreetbikes.com/9200.../Dugs_YPVS.jpg

hmm!

i should have a bit of time yet to do some stealth bombing before Nath's big bore is on the road and running.. would be good to blow him away with my '250' and make him feel bad about his bike after all the work he has put into it

[g0zer]

i have learned something new about syncing carbs, have tuned the mixture screws individually this time rather than both at the same time.

it absolutely RIPS when it comes on song now but only in the lower gears?!?

i think this is what is happening:

when i am in the lower gears 1st through 3rd- as i feed throttle it hits the powerband then takes off like a rocket.

however in the higher gears especially 5th and 6th- i want WOT or close to it. In the lower gears of course, there isnt wind resistance to overcome so im not needing WOT to get the motor to pull.

When i WOT the bike it bogs down- especially at 6000-8000RPM, between 9000-10000RPM its not quite so bad but if i roll off from WOT it definately pulls harder.

i have read that the main jet controls 7-8ths throttle to WOT, so now think i have a main jet problem?

i know jack about jetting and carbs apart from what i have read, is my diagnosis correct?

if so, do i need to go down a jet?

i have pulled the plugs and they were a bit carbon'd up. In fact i 800 gritted the terminals as it was becoming difficult to start and now it starts easy again.

[ritza]

if its bogging down at wot then youre too rich on ur main jet, but there will be a trade off at the mid range with some fluttering when it goes onto main jet...its called the 6k stumble ...fine balance between the two. and you should set the carbs up as on two seperate engines