vm28's on an xs360

aus_xs360

aus_xs360

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Hey everybody,
I'm in the process of building my first brat/café racer from a donor xs360 I found in a mates dads shed. the bike was pretty grubby but mechanically sound. the only thing I've really needed to replace was the carburettors as one had a seized up slide.

I originally put vm34's on after some crappy advice and as to be expected they were insanely rich regardless of significantly reducing the jetting. :banghead:

I've now ordered a set of vm28's based on some advice I found on another forum thread but the shop has no idea what jets to order with it given its not a very common bike.

does anyone have any suggestions for jetting sizes for this bike with these carbs?

Cheers!!!!
 
Still too big for a 360 in my opinion, but you should be able to get them to work. Most people that have tried them on here have troubles and then never return to say if they got them working or not. That usually means they gave up.

I would check with the honda guys that use them on the same size motors, you'll probably be able to get closer to a baseline jetting with their info. Most likely you will want to buy a few sizes bigger and smaller just in case. Big $$$ getting aftermarket carbs to work, it's just the way it goes.

Once you do get them right, you'll be happy you went with them. Throttle response is instant compared to CV carbs.
 
Cheers Wolfe!

looking at what the CB360 blokes are running the 28's should run well, pre-jetted vm's and jetting kits are way more common for the CB's. No one seems to know anything about xs360's though.

I'll post the outcome of the jetting here, this is basically the last stage of my build (minus some cosmetics) so no chance of quitting!!!!:D
 
Hey Muse,
I've been rebuilding the xs360 over winter (Aussie winter) so haven't really progressed with the carbs. will have them on and tuned by December hopefully so once that's done I'll post about it including full jetting specs etc.
 
You can buy rebuild parts for the stock 360 carbs.. have you tried soaking them in some kind of solvent first? I wouldn't give up on them yet. The pricey part on the 360 carbs would be the vacuum slide part, but then you'd be able to keep the stock tuning. You'd probably be a lot deeper if you went with those VM carbs.
 
Hey Mike, I didn't really try any solvents other that degreaser to clean them. But the slide was stuck pretty hard and some local bike builders told me that its probably no good anymore. besides the bike is running pods and shorty megaphone mufflers now so needed re-jetting regardless.
 
Oh Damon, where to start....

I got the bike running, but really rich. Worked out the pods I was using were way too small so replaced them with some top notch K&N filters and seemed ok. I even ran it on a dyno.... that's when I worked out it wasn't just running rich, it was burning oil...probably should have done a compression test to start with:banghead:. Didn't seem to be too bad so I decided to just ride it for a bit as is.
Got a few good rides in but after a 100km ride I did on a nice late summer day, it was running very rough. I decided that it was time to do a top end rebuild. Very very luckily a Yamaha shop in my town actually had OS pistons and rings! cost me $500 in total which was as much as the bike cost me!

I've now had the head refurbished, cylinders bored and honed and I've put it all back together....checked the compression... 75psi both sides. WTF!!!!
I'm going to do a leak down test tonight, the valves are all like new so I doubt they are the problem. it also has new gaskets so I doubt the as the cause. I suspect the rings haven't seated right... open to suggestions if anyone can think of any other sources of the leak, bit of oil in the cylinder will hopefully give me some insight.

in regards to the vm28's, at mid range and fully open they are amazing. definitely give my bike an extra kick. low range is a bit more tricky to review, specially with the burning oil. once I sort out this compression issue I'll be able to give a much better review and detail of the setup (e.g. jetting etc).

Hopefully I'll have it sorted soon, by the end of winter at least!
 

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Did you give the rings a chance to wear to the cylinders and make a good seal?

When I got my bike started for the first time, I got the engine running stable and then I full throttled 1st, 2nd, and 3rd gear a couple miles

You have to ride the bike under some moderate load, you cant just start it and rev it a couple times. Get on it and rip it lol
 
Hey NHMike,
you've hit the money on the head. I just finished reading some triumph forums and I think I've worked out the problem. the 75psi is WITHOUT the engine having actually been started. I think by running it dry (i.e. not having put any oil down the spark plug to get that temporary seal) I'm not getting enough compression for the engine to fire up. could also be the timing isn't close enough to fire up as I forgot to mark the exact position for the timing plate :banghead:
Anyway, you're most likely right, the engine needs to run for the rings to seal. engine hasn't run and thus no seal=no compression. this would explain why the psi is almost exactly the same on each side and why compression is low when it has new valves + bore and honed cylinders.

I'm also going to take this opportunity to also mention this is the first time I've ever tried to do anything on a bike/motor vehicle other than change oil, and I don't know any mechanics. so I'm very much a newbie and learning as I go. :umm: Lots of fun and frustration!
 
You need to set the static timing first. Dont keep turning the engine over if you dont plan on starting it..

Do static timing first, pour some gas in the spark plug holes, try to start it.

Setting static timing is pretty easy you just need a circuit tester thingy
 
That will work. That will tell you when the points ooen up based an the position of the crank. Turn the engine counter clockwise without the spark plugs and stop directly on the LF mark. Do not go past the mark and turn the crank back. Then you can turn the points plate right to where its supposed to open and th circuit light will turn on. Must have ignition on to do this. Well thats how you start the procedure...
 
thanks Mike, I watched a whole bunch of vids on setting timing last night and read the manual. will get it done this weekend, spray some "start ya bastard" done the carbs and with a bit of luck hopefully that will do it! will report back after the weekend with progress.
 
mission update: the points were being a pain so I decided to replace them with a Pamco ignition. massive difference! once wired up the bike started straight away and runs beautifully!!!
This weekend I'll run the engine for a bit and then start on tuning the carbs. spring is only 3 weeks away here so the clock is ticking!
 
aus_xs360 said:
mission update: the points were being a pain so I decided to replace them with a Pamco ignition. massive difference! once wired up the bike started straight away and runs beautifully!!!
This weekend I'll run the engine for a bit and then start on tuning the carbs. spring is only 3 weeks away here so the clock is ticking!
Click to expand...

Spring :D we are almost done with summer..........................funny how it works.

Glad the Pamco worked out!
 

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