Single Carb conversion on my XV750 [Virago] Bobber - Trials and Tribulations- Ep2
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- čas přidán 30. 04. 2022
- Hey guys, been meaning to get around to a follow up video on the single carb conversion and where its at atm. I've had alot of questions via social media about it so i figured id make a little video on the issues etc i've been having.
Comment on what you think i should do. Cheers guys! Matt. - Auta a dopravní prostředky
![Moto Camping my [Virago] XV750 Bobber in all the wrong places! Mudgee trip Episode 1](http://i.ytimg.com/vi/3vDY1lGYtng/mqdefault.jpg)
![Seat [Budget Bobber] ENG](/img/n.gif)
Matt, you know you're the first person to've put together some sensible, informative and painstaking videos on the fitting and running of these single carbs for the XV. I FELT YOUR PAIN!
There are a ton of rushed, 2 minute wonder videos out there of installations, and guys are still taking peoples' money selling their junk manifolds, but they provide ZERO videos illustrating them running successfully, which proves the point that the XV's engine just isn't designed for this set up. I tried 2 different manifolds and both were shite, it looked good, idled nicely but ran like a disobedient PIG. I reverted back to the twin carbs without the AIS system and pods, and the bike forgave me, it runs so much better. Word of advice to anyone out there still thinking of doing this job ; aesthetics aren't everything, just keep hold of your money.
Enjoyed watching your hard work on this buddy. 👊
Hey mate! Thanks for the comment.
Totally agree! The amount of crap manifolds that some Joe has made and just says “Goodluck” lol.
The most efficient way to feed these engines will always be twins in my opinion.
My cafe racer runs so damn good on twin VM34s.
Have you tried a KJS manifold? I honestly have heard that those manifolds are the only way to properly run a single carb on a virago. Hesitant buy one as they are pretty bloody expensive.
Might try one in the future. I always know I can go back to my 34s
@@mattfranco8715 I was seriously tempted by the KJS manifold, but I think there was a question mark over whether the owner was still in business...
Also, there was only one person on CZcams (Thad Mandin) who showed the KJS system fitted to his bike, but again, he ONLY demonstrated the engine idling, NOT driving smoothly up through the gears, full throttle, backing off etc, and I believe he then sold it on...
I sank about £250 into the "SmithTech" (Adam Smith) "y" design manifold and Mikuni carb, nice welds, but who the f*** needs nice welds on a system that simply doesn't work. The weight of the carb sagged on the rubber boot, the weird design was all wrong... Compression was fine, but there was nothing my mechanic or I could do to get it pulling nicely without it lurching, coughing and spitting, even with a support bracket made up and different jets. I then bought the searayguy "v" design manifold from eBay, which had shockingly rough welds, which had to be smoothed out inside with a sander before installation, (!) but even then only performed very slightly better, it still spat and sputtered.
Both rubbish. Super pissed off. Just a load of money wasted and a world of pain.
I know these guys will continue to argue until the blood runs out of their faces to tell people they're fitting it all wrong, but until they can get off their lazy backsides and actually make the effort to make some proper videos installing -and more importantly *properly road testing* their manifolds to prove their beloved designs really work, no-one will ever be convinced. Until then, the original twin carb set up for this machine will always rule.
So glad you got your bike running well again! 🤘
keep at it mate. I feel like I read more woe than go with the single carb setup. Looking forward to seeing what more you have planned on the cafe!
Yeah same here. Honestly it felt great when it was going good.
Yeah I’m keen as for the cafe mods!
I've never seen a man suffer so much with changing spark plugs hahahahah. Great content as usually can't wait for the next one.
Hahahah! Cmon mate! I burnt me leg 😂😂.
@@mattfranco8715 hahahah
Very late to the party. But I like this sort of content! Also trying my hand at building a bike. Been riding for around 10x years, first time building my own. Have done the simple mods grips/exhaust/levers/paint. This time I was basically gifted an xv750 81 and sx650 79 [I think] planning to Cafe/Scrambler/Streetfigher build them up. Thank you for the ideals, suggestions and help! Please do as much as your heart desires!
I’m glad you like it :).
That’s so good you got given the bike!
You’re welcome mate. I’m glad you’re getting something from my vids :)
Rock on man nice maskin
So I will also tell my experience with a single carb.. I made a single aluminum manifold and used a bst 40 carb from ktm lc4.. The engine needs to be warmed up and driven with an open choke for about 4-5 minutes at temperatures of 10-20 degrees Celsius. .when it warms up it works perfectly but only up to 110 km/h. I guess I need gas so I will experiment with the jets.. Then it gets confused and won't go any higher.. Sorry for my english .. Keep up the nice videos
Great videos. I couldn't get a single carb working either.
Punish isn’t it.
I do want to try again but on my cafe racer this time and build the manifold myself. One day.
Hello Matt as far as I can see you having some pups and hicks on your bike. Well that is because you are using a rubber mounted manifold. The rubber does not transfer a heat to the manifold and it always stays cold. In this situation you always gonna have a rich mixture no matter what jetting is. On single carb conversion the way of fuel to the engine is much longer than on dual carb set up, so manifold should be heated as much as possible. Second thing, your jetting should be around main No 105-115, pilot no more than No 40 on 35-38 mm flat slide carbs. Spark plugs should be R5 heat range as well. However at the start point bike should be warmed up on choke with no throttle at all till normal temp. This is always with single carb on cold start. Very important... Manifold must be aluminum and bolted to the cylinders to be heated for normal fuel evaporation. There is no other way to have a well running engine. Check this out. czcams.com/video/PyKKHSenpFo/video.html Hope you will make it. Best regards.
Very interesting mate. I never thought of that. I might try and make my own manifold again at some point and see if I can make it work.
The KJS manifolds are super expensive so I might just try and make my own haha.
For now my twin VM34s on my cafe racer do the job and do it well so I’ve got no real desire to try a single carb atm. IMO the twin VM34s are such a nice operating and easy to tune carb, I’ve had almost zero issues with them.
The accessibility is great too compared to my VM36s I had on my bobber. They were abit of a nightmare to work on if you needed to tune them.
Well yes KJS is expensive, but works well and they made the way they should be made. I m sure money is not paying a big game here. Maybe yes... You can also buy VTC Motors manifold that is made same way... It is actually my product. However I just want everyone to ride their old timers and have a fun. Don't let them rot in the barn. Cheers.
Oh yeah I’ve got no doubt they work well. There’s always glowing reviews which is why it’s so tempting!
Oh really? Do you have a link to your manifold? Thanks mate.
Cool bike!
Thankyou! Cannot wait to make more vids on it! Rode it last night and enjoyed it so much. Hopefully I can hang on to it for a lot longer.
I'm running a kjs single intake on my xv1000 and couldn't get the mikuni carb to wor k well like you. I am running the stock front carb from the dual setup and bit works fantastic.,no rejet just stock.
Yeah? I definitely think the manifold design is the reason. It prioritises the rear cylinder a fair bit.
That’s interesting though. Maybe down the track I’ll have a look at one of those manifolds.
Is that a BST40 or a hitachi carb?
I’ve got both in a box somewhere.
The KJS has worked great for me on my VStar 650 once I got the TPS problem worked out.
Yeah I’m at the point now where I love the twin VM34s enough to keep them. They do they job great and I don’t really have issues with them. Stoked for you but!
Found your next instalment. I think you came to the same conclusion as me.
That rear is far more biased for flow.
From what I'm seeing pretty much all single carb setups smash the fuel against a wall before the runners split. This mikuni one is like my design I dismissed for this reason.
I've designed a few different ones which we are trialing see how they perform.
Haha! Yeah I’ve still got the kit and I’m even tempted to have another go myself. I built a manifold for it awhile back and it was the same outcome. I thought with a manufactured one the issue would be resolved but nope, same problem 🙄.
I’ve got a couple engines laying around so if I get bored enough I’ll make another one.
What do you think about the KJS one? From the looks of it it’s equal but still the flow to the rear cylinder looks prioritised.
@@mattfranco8715 if it was a chamber, I'd agree, but with the split down the middle like it has, I reckon that would help. I'm going to try design one that wplits like that and improve on it.
Thankyou mat real enjoy your vids . very educational . sad to see ithat single carb and one sided manifold didn't work out to well : but never no success with out Failure... and if you hadn't Tried we all would have never known Thankyou ... But I recon if the carb would of been on left of bike the front cylinder would of got the most gas due to distance and flow of gases ...also carb so far out in corner's very prone to floats would ride up and down n flood ... I owned my xv 750 1994 for 3 years and I could never stop front cylinder being starved of fuel in float bowl vapour locking . every single time I rode it Hard it broke down ...after removing carburetors n recalibrating float levels and jets 3 times .I finally realised . why didn't my xv 1100 ever have this fault ... Turns out all xv 1100 s have a electric fuel pump... fitted one to mine now and NO probs since ... Great bids look Forward to seeing How your cafe racer turns out Have a wicked Christmas's n all the best for 2004 ...
Ohhhhh, true. Very good info. It’s good that you figured it out haha.
Yeah I do want to have another crack at the single eventually. It still appeals to me for sure. But I would design and fabricate my own manifold.
I have the kjs but is not good with the VMs... Start fouling rear plug and black smoke even with 15 pilot..
Also, use BPR5ES plugs when using single carb set up.
I'm trying this weekend a CV carburetor and hopefully works cause for some reason I can't get the twins running good.
Yeah I tried 5s but they didn’t seem to improve it at all.
I may have a tinker with it again one day soon.
Let me know how ya go with the CV carb!
Errr yey all the best for 2024 ...
Thanks mate! You too.
A mi me sirvió la conversión.
Solo que la aceleración hay wue ser discreto con la mano y mi prueba hace años en una ruta de aproximadamente 500km solo una falla y fue el filtro de aire que se salió..! Pero mi virago 1100 año 1998 colocandole las cajas de aires y usando mangueras en sus agujeros del chasis ?
Quedó perfecta luego le meti 1500 kilometros y es una maravilla
TM38 carb and jetting you describe sounds like a 2 stroke/snow set up what jetting ,slide and needle are in vm34/36's ?
I really like your rear fender and seat set up the back looks tidier compared to other xv bobs what fender it this or did you cut it down from something else? Also curious if those are stock size tires and did you Lower the rear or just front
Thanks bro! Yeah all the bobs I’ve seen I didn’t like. I saw one on a Insta page I think they might be in Germany or something and they just bob everything. One day I stumbled on a virago bobber they did and fell in love. Had to do it.
It’s a Harley rear fender that I cut down :)
Yeah just the front :) miss that bike 🥹
Do you think that two TM38 would be to big for the bike? I’m thinking of giving up on my single carb setup with a single TM38 so wondering if I can just buy another or need to get two TM36. We’re you recommended to get the VM36 size.
So sorry for the lazy nearly 2 week on reply 😮💨.
Nah I’ve heard of people have great success with twin tm38s.
I think if I attempt the single again I’m going to by a different manifold. There’s a certain design I see everywhere and seems to work.
Visit mikunioz.com for your carb kits etc. they are awesome :)
Great looking bike. There's a gentleman "Hammer Head Garage" who converted to a single with a VM30 Mikuni and he's used this for the past few years now. This is on a XV1000, maybe check out his channel, seems like a smaller carb may be the trick on these bikes? I'm going to be giving that setup a shot. Check it out! Thanks for the great vids! Always appreciate your workmanship and perspectives. Cheers
It’s funny you say that! I actually made my own single manifold and bought a VM30 because of him! Haha it didn’t work and I blamed my manifold but essentially it was doing the same as what the TM38 is doing.
So I know it can be done but I just kept weighing up how much time I was spending tuning and trying new things vs how much I was actually riding it haha!
Thanks so much for the feedback! I really appreciate it. I’ll do my best to keep them coming!
Lo que pasa es que no saben como hacer las cosas y aún así les meten mano a las motos, tampoco tienen paciencia, y lo unico que hacen es tirar mierda, pónganse a investigar, y tampoco lo hagan si nontienen el dinero suficiente, para que no anden llorando como niñas
FWIW, the KJS setup uses BP5ES front and rear, I ran that in my 83 920, but then went to the iridium equivalent and never had an issue again
Yeah I’ve hung onto the carb setup. Very tempted to buy the KJS manifold. I think the manifold design is 100% the issue.
Definitely
Chuck one of the old carbies on the single manifold. That’s what a lot of the Americans do, one vm36 should feed it fine.
Yeah that was definitely an option when I was making that video. But honestly as far as the bobber is concerned, I’m done making changes on it. It’s running great so I’ll leave it alone now and use it for something else.
Hi Matt just spent the last month trying to tune my 1998 yamaha xv 750 virago single carb conversion. Mikuni oz a tm40-6 front cylinder was always lean would backfire through carb every so often
so i made a plenum divider out of tin and put it in the manifold now runs fine, i think the manifold is a bad design
Hey mate! Yeah it was a battle getting mine to run right. I agree it is a poor design. I’m curious to see how you made the plenum divider thought!
The kjs for the 1100 suggests the bpr5 es plugs
Yeah I tried 5s for abit. Didn’t make much difference.
Hello There, How much $$ for the motorcycle if you were to sale it ? I really enjoy your videos. Great content of information and well presented. Thank you very much.
I’d probably sell it for $6000-7000AUD.
Oh that’s good to hear thanks mate! I appreciate that very much! More vids coming very soon!
Hey mate. Is the 22.5 pilot and 230 main the best jet setup you found?
Nah mikuni Oz recommend 15 pilot and 200 main as a starting point. But I got that info after I had already taken it off.
They sent me the carb with the wrong jets for the kit that I ordered.
Hi, thanks for the info.
Many people run a hotter plug in the rear cylinder with singlecarb, they go to a "6" instead of 7 for the rear, not that I like the idea, I too tried the singlecarb and went back to dual, but fouling rear plug is very common with singlecarb on these Viragos.
What manifold is it, it looks like the one from Mikunioz?
Yeah I didn’t mention that but I actually tried that too! Even tried a “5” which I quickly took out.
Yeah mikuni Oz manifold. I’m happy she’s back to running good on the twins. Big fan of them. They are beautiful.
What twins do you have?
@@mattfranco8715 Thanks, I have bought serveral kits for different bikes from Mikuni Oz, even that I live in Denmark, I was hoping their singlemanifold for XV engines was better then the rest out there, but I can hear their manifold have the same problems like all the others.
Right now I have dual VM38 on a1100 with high compression pistons and high lift cams, the VM carbs works just like they should, nothing bad to say about them, other than I would like pumper carbs instead to get the crisp throttle response.
I have bought two Keihin FCR39 that I will try out during the summer, to get the acc pumps, but I don´t know how it will turn out.
That’s awesome! Can I ask where you got the cams and pistons from? That’s something I’d love to do to another engine I have for a future project.
@@mattfranco8715 Hi, I got cams and pistons from Pacific Coast Star, US. They are for XVS1100, cams fit right in (needs other pistons with higher compression and more space for valves). Pistons are the same bore, but they are not a straight swap in the Virago engine, for several reasons. The XVS1100 have nicosil lining in aluminum sleeves, it is extremely tough, but therefore pistons rings are different than rings for steel liners. And XVS1100 con rod are longer, so Virago con rods are no good for XVS pistons, the holes in the pistons are offset.
On my bike I have fitted XVS1100 crank, con rods and cylinders, Virago heads, XVS1100 high lift cams and hc pistons.
Engine block needs bit of work, the XVS cylinders needs a slightly bigger hole in the block.
The XVS1100 cank and con rods, also found in BT1100, is lightened a lot, they weigh 20% less in XVS1100 compared to Virago, and that makes it quicker to accelerate, and less mass that have to stop and reverse all the tome, fewer vibrations and lower fuel consumption.
You can really make a killer engine with these parts, but it is not cheap :-)
So would you recommend the vm38 single for someone who rides very little or the twin vm36/vm38
Honestly. Twin 34s. I’ve got 34s in my cafe racer and they never let me down.
The idle adjustment and air mixture screws are positioned perfectly for on the fly tuning where as the VM36s are facing inward and abit tricky to access. I’ll attack the single carb setup again one day I think and probably just run a large roundslide carb or a HD carb.
I want to design a manifold that works with shelling out millions for a KJS.
I had the same problem,it is ignition related. Take the resistor out of the spark plug cap or if you can get non resistor spark plugs like they originally came with,otherwise you have 5k ohms resistance in the plug cap and 5k ohms resistance in the plug. that is too much,its out of spec. I can't get non resistor plugs here in Canada so I took the resistor out of the plug cap and replaced it with a piece of brass. The bike starts better,has better throttle response and does not foul the front plug anymore.
Yeah done that :) yeah I only use the non resistor plugs :)
That’s sick but!
have a nice wekend rock on my bick work nice
By chance can you tell me how I go about mounting two vm 30s to my 700 like where do I get mounting boots?
Yeah, you should be able to get them through Mikunioz.com .That’s where I got everything!
Goodluck with it all!
What was the name of this conversion kit that you used I'm very curious because I'm about to purchase one
Sorry for the late reply. It was just a single carb conversion kit for a 750-1100 virago on mikunioz.com
Air filter looks a bit on the small side for the air it would be sucking at higher revs. Why not just put a much larger filter on it first to see if that helps!
I think I ran it without the filter a couple times with no change. I don’t own that bike anymore unfortunately.
hice la convercion a un carburador..mi yamaha vstar650.....funciona muy bien mejor diria yo....solo un problema...al apagar motor bota conbustible del carburador solo aveces...como puedo sulucionar esto amigo....
Sounds too rich on the idle jet maybe? Does it foul plugs if it just idles for awhile?
Converted my virago 700 to single mikuni vm 30 anyone know why my rear cylinder exhaust gets cherry red front one doesn't get red
Sounds like your rear cylinder is running very lean.
What intake manifold do you run?
The vtc motors one on eBay bolts directly to motor no boots it's confusing me cause I figure both cylinders should be cherry red being that they are getting same amount of fuel with a single carb setup
Sorry for the late reply, for what ever reason I never get notifications of responses.
But yeah I’d say it’s all manifold related. The manifold game is a fine art. If it’s not perfect, it will never run right. That’s why people swear by the KJS manifold.
I’d start with the basics and check compression and spark to make sure they are not a factor, then I’d be trying other manifolds.
Well I did get the rear cylinder not to be cherry red I put a 62.5 pilot 320 main now I need to lean it out at idle but I'm happy it's not running lean now
Como são os gigleus?
Hey there, I’m not sure I understand?
u nead to short down u exhaust but still use the bufflers
Do I? That bike ended up with the VM36s on it and ran like a top.
Ive sold that bike now anyway. Wish I didn’t have to.
our trottle cable is in total wrong posision
You think? I tried multiple positions. Seems to hang up regardless of what I tried. I still have the kit. I may one day try it on the cafe racer. I sold the bobber recently
The valves are shot
If you happen to still have this single carb set up laying around, another CZcamsr (Steve's DYIs) looks to have solved the virago single carb air/fuel cylinder imbalance. It's to do with the cylinder firing order. He used a different intake from what you used, so I'm very curious how the MikuniOz single intake would do with his fix.
I was about to pull the trigger on some dual vm or tm38's for my xv1100 until i watched Steve's video. Gives me hope for the single carb setup.
His video was just uploaded a few days ago...
czcams.com/video/u-LvZgdkaPg/video.htmlsi=djrsuPSeFXCW44S5
Nah I don’t. I ended up selling it. Man I love that blokes videos. He’s a weapon. I’d definitely be keen to fiddle with a single carb setup again in the future and see if I can make it work in my cafe racer
Small carb. Try a PWK 35
Ive since sold that bike but honestly others have had success with that carb. I still think it’s manifold related.
The thing absolutely hammered up top with the single carb. But constant dramas fouling that one plug.
I’m interested to do another conversion on my cafe racer and just do a KJS manifold.
Sell that one and try the "Mikuni vm38" there better for the viragos
Unfortunately I don’t have this bike anymore 🥲.
But yeah honestly next time I go single I’ll prob get a round slide anyway.
u need bafflers on u exhaust
It has 2x 15inch baffles. 1 in each pipe
Bolt a s&s carburetor to it
Sold the bobber a while back now :(
u buy a fack carburetor.
Did you mean fake? No, it’s a genuine TM38 Mikuni.
pink gay
What?
@@mattfranco8715 sorry drunk