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Discussion Starter · #1 · (Edited)
Recently traded for a 1982 Yamaha 920J Virago. This bike has plates from 2005. Cleaned and kitted the carburetors and changed fluids on bike. Rebuilt front wheel cylinder. New battery installed. It seems starved for fuel but a shot of starting fluid in the main intake fired that sleeper right up.........only did the bench sync and 1.5 turns out on idle mixture screws (new with o rings). Then it was helmet and glove time. WHAT a monster to hang on to, I kept the bike in first gear just to check all this out at a lower speed. Lots of popping and some backfires but the torque was crazy (both cylinders firing). I worked the carbs on and off the bike 4 times so far, just finding Steves DIY youtubes helped. Mixture control valve was already blocked off (and yes it tests bad). The rubber boots that mount the carbs to the heads are about $15.00 shipped WITH new O-Rings, it turned out the O ring to the front cylinder was aftermarket and was not thick enough to seal and lots of air was getting in the flow path. You can buy the correct O ring and WAIT for it to arrive. I made a gasket in 5 mins and hi temp RTV'd it to the front cylinder carb port (doesn't slide about, helped in remount)...installed the allen head bolts instead of the OEM's torture types. Installed all stainless steel bolts in carbs also where handy. Was getting dark then, so today I will check for air n vacc leaks. At least it runs now. Have a single carb manny coming soon. I think I better get me a scooter to practice on till I get my brain and body in shape for this real cruiser.
Tire Fuel tank Wheel Automotive fuel system Vehicle
 

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Discussion Starter · #3 · (Edited)
Recently traded for a 1982 Yamaha 920J Virago. This bike has plates from 2005. Cleaned and kitted the carburetors and changed fluids on bike. Rebuilt front wheel cylinder. New battery installed. It seems starved for fuel but a shot of starting fluid in the main intake fired that sleeper right up.........only did the bench sync and 1.5 turns out on idle mixture screws (new with o rings). Then it was helmet and glove time. WHAT a monster to hang on to, I kept the bike in first gear just to check all this out at a lower speed. Lots of popping and some backfires but the torque was crazy (both cylinders firing). I worked the carbs on and off the bike 4 times so far, just finding Steves DIY youtubes helped. Mixture control valve was already blocked off (and yes it tests bad). The rubber boots that mount the carbs to the heads are about $15.00 shipped WITH new O-Rings, it turned out the O ring to the front cylinder was aftermarket and was not thick enough to seal and lots of air was getting in the flow path. You can buy the correct O ring and WAIT for it to arrive. I made a gasket in 5 mins and hi temp RTV'd it to the front cylinder carb port (doesn't slide about, helped in remount)...installed the allen head bolts instead of the OEM's torture types. Installed all stainless steel bolts in carbs also where handy. Was getting dark then, so today I will check for air n vacc leaks. At least it runs now. Have a single carb manny coming soon. I think I better get me a scooter to practice on till I get my brain and body in shape for this real cruiser.
View attachment 152197
I should have compression gauge arriving today, I think 135-145 psi is average per cylinder. Also 5 PCS 5K VARIABLE RESISTORS UNIVERSAL CAR 10 TURN ADJUSTABLE RESISTOR NEW IBVR | eBay is a five pack of variable resistors (adjust to 1K ohm works) THIS attached between battery positive and the battery low sense line will clear up that WARNING BATTERY light. New carb boots ordered also BUT I highly recommend making your own intake gaskets and hi temp Permatex them to the cylinder head. If your O RING has failed (or your not sure) DO NOT run down to a hardware store and FIND one.....A. Vitron O-rings are out there. B. BUT harder to find and make certain you use the correct thickness for the boot it will fill the cavity totally, I keep finding o rings aftermarket that are TOO narrow and will NOT seal (you will be MR LEAN) Exhaust gasket material is available at most auto parts shops and is not expensive. I would try this BEFORE removing carbs....you can loosen the boots and slide your hand made intake to head gaskets......try to fire it up then and check for air/vacuum leaks with choke cleaner sprayed around the carbs while running. Any change in engine rpms will be the clue that you found a leak. All those lines and hoses temp plug them at the boots (leave the vac line that attaches to fuel tank, else primary petcock may not open.) I found that the pilot mixture jet (for idle) beginning settings is to lightly close then back the screw out to 2.5 turns each. IF you decide to clean your carb jets, welder tip cleaners are useful BUT a high E steel guitar string will fit all the openings and is NOT abrasive. You can clear every port and jet with a can of carb cleaner and the piece of E string. Study all the passages and block multi exits and check EACH is clear and cleaner will pass through. There are many great youtubes on this exercise .......Steve's DIY are well done. You can sharpen the carb spray tip you can even remove it from can and heat it with lighter then use needle nose pliers to stretch the tip to narrow it's opening then cut to fit ALSO warning a little tape wrapped around near tip helps seal your port/jet as you spray (CAREFUL not to get that carb cleaner in your face) IMHO the dynojet kits for the virago is well worth the costs and include parts that are not easily sourced.....the cost $85 each but rare parts tend to get costly.
 

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Discussion Starter · #4 ·
As far as mods...... new tail, seat, front forks n clamps, super low mongoose handle bars, pull off the fairing/bags and install new clutch/brake controls. Tank will be considered first....also DC to DC 12V Block 70watt converter installed to keep steady power on ignition system module. This makes for 1-2 turnover starts even on 17 degree mornings. Highly recommend this device ($25). It takes a huge load off the entire starting system and should keep all those parts from being stressed making them last (much) longer. Youtube Steve's DIY virago vids he has one on installing the block converter. I am a retired electro-mechanical engineer and know how well these block converters keep a steady source reliable. Even if your battery dips to 11 Volts during startup the TDI/CDI will maintain the correct power to keep a hot spark.
 

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Discussion Starter · #5 ·
Just came in from garage, now that I have ridden "the beast" something seems heavy in the steering. Fairing is scuffed and small ding in right side top of tank. How do I check if the stem is bent without tear-down?
 

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I would be very surprised if the stem was bent without the wheels and forks and basically everything else being wiped out by that amount of force. Someone might have squeezed the stem bearings too tight or something I suppose - I'd lift the front end off the ground and play with the steering and if that didn't tell me anything I'd just pop the front end off real quick and check.
 

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Discussion Starter · #7 · (Edited)
Turnip I got a bike lift and REAL compression gauge 142 and 147 psi (front/rear) ALSO the aluminum single carb intake arrived and it was needing RTV hi temp gasket sealer and prayer to get that thing to seal at the heads. I am using the front original carb and am getting back fires through the carb BUT the engine now runs on both cylinders finally.....
I will hang the bike tomorrow and check out the front end. I can see the bike has been dropped (a 1982 must been dropped at least once) and there is a minor ding in the upper right side of tank...also replaced the petcock (was leaker). PROGRESS!!! sat and adjusted idle mixture but didn't notice any change then found crankcase vent was open plugged it and zipped. Then tried to set idle mixture sweet spot but .....seems like there is trouble in that circuit. Never found any engine difference while adjusting. I may just get a TM40 carb to replace this one due to it being 40 years old and STICKS out kinda far. This Virago is housed at our beach property and I will only be there 1/2 the time.
 

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Discussion Starter · #8 ·
Tomorrow, will exchange bowl floats with untouched settings into this new FRONT carb, btw it does heat both heads evenly, I do have a set of 2001 VStar 650 carbs I can work into this if it helps. BUT those carbs breathe above, who knows maybe it can work with a bit of flubber!!!.
 

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Discussion Starter · #9 ·
BTW BIP Single Carb Manifold.....hi temp rtv one gasket to head using mucho red stuff on one gasket on HEAD side of gasket.....tighten up THAT side till the goop just starts to get squished THEN let it set over night....tighten it just snug.....THEN do the other side that way....
THEN tighten just to squishing out a bit and let dry AGAIN over night....(MY GARAGE was 45F so maybe yours is better). AFTER it is cured you may open it and clear any excess from intake coming into cavity.


Tighten any fasteners left to similar torques by touch. Boot n Carb n Go (well nearly... adjust carb as needed or REPLACE that old tired dead unit with a TM 40 (thinner).
 

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Discussion Starter · #10 ·
BTW BIP Single Carb Manifold.....hi temp rtv one gasket to head using mucho red stuff on one gasket on HEAD side of gasket.....tighten up THAT side till the goop just starts to get squished THEN let it set over night....tighten it just snug.....THEN do the other side that way....
THEN tighten just to squishing out a bit and let dry AGAIN over night....(MY GARAGE was 45F so maybe yours is better). AFTER it is cured you may open it and clear any excess from intake coming into cavity.


Tighten any fasteners left to similar torques by touch. Boot n Carb n Go (well nearly... adjust carb as needed or REPLACE that old tired dead unit with a TM 40 (thinner).
Went out and worked on the intake again today..it is tight to the heads and found air leak where carb boot attaches, had new boot on hand and replaced....still leaked......... OK what could it be being that I rtv'd and homemade gasket in there.....THE DARN screw clamp (like a hose clamp) while closing clamped into it's self blocking any further tightening (screw felt tight) but was just bent down to far. I reformed it AND changed everything to the other carburetor (old rear carb). The float bowl overflowed so I guess it needs polishing or adjustment of set level. But I turned off the RESERVE and to PRIME so the engine vacuum has to be on before fuel flows. IN ANY INTAKE LEAKS, gaskets/rtv/clamps and even boots are better to just replace at the start on a 40 year old rocket.
 

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Discussion Starter · #12 ·
Dropped on lawn turning around, right front turn amber lens DOA else I was lucky. I got it recovered and put it up for now. Rain coming anyways.
I should adjust those UNIQUE handlebars to give some leverage, the bars are set to narrow sweep back and to me is not useful. When puppy is full runner I will get some better from Dime Cycle. Oh, and order also a front turn lens.....
 
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