Carb Rebuild Opionon

cpotts454 · Posted: April 1, 2009, 8:42 pm Post subject: Carb Rebuild Opionon

Whats your all's opionon on rebuilding carbs? Do it yourself? Pay someone localy? Pay the guy that does it on ebay? Or just buy new ones?

I've pretty much narrowed down my rough idle and hard starting on a carborator issue, I just dont know what I am going to do about it. I cant really afford much more then $100 to do it.

tacoswild · Posted: April 1, 2009, 8:56 pm Post subject: Re: Carb Rebuild Opionon

One vote for do it yourself. It's not that complicated but it can take more than one try so people get frustrated. Basically you've got three or four shiny brass parts that are jets, easy to spot em, they come out with a flat screwdriver (or just pull out for the needle jet). Clean em and write down the numbers you see on them. Probably need a little magnifying glass for that. Spray carb cleaner down every passage you can find on the carb and chase with compressed air. If the numbers on the jets don't sound wildly out of line from stock put em back in. Check float height and diaphragm for tears and reassemble with a new gasket. Done except for fine tuning now.

cpotts454 · Posted: April 1, 2009, 10:02 pm Post subject: Re: Carb Rebuild Opionon

Well I've rebuild them before but I believe I might have more damage then I fixed. I am really leaning towards buying a new set. I dont know wheather I should be another set of the same carb so I can always have spare parts, and then get them rebuilt professionally, or should I pay the more money and get the VM carbs, in which I have no idea how to tune them or what jets to buy for my performance enhancements. I am sooo lost.

woodman · Full Member Joined: Oct 12, 2008 Posts: 256

I rebuild them myself, but only you can decide if you want to learn and have the confidece to give it a try. Its not rocket science but you have to be careful you dont lose parts & remember how it goes back together. Youll never learn paying someone ellse to do it.

pumps · Posted: April 1, 2009, 11:48 pm Post subject: Re: Carb Rebuild Opionon

I'm always for DIY if you can. I would be out of my other business if everyone did though.

grant · Posted: April 2, 2009, 6:59 am Post subject: Re: Carb Rebuild Opionon

My '76 had cold starting problems. Bought new coils, didn't help. Checked plugs and they were clean with what I assumed to be a decent spark. Rebuilt the leaky carbs, no improvement. Rebuilt another set I had lying around, tried the old, tried the new, with air boxes without airboxes and the thing just ran like crap. After a month of total frustration I took the bike to a flattrack guy who has had a shop in town for 40 years. Turns out my problem was simply a set of crappy points. Hated to give up and take it elsewhere for work but it sure finally fixed my problems. I'm not much of a carb rebuild guy but if you take your time and pay attention you can rebuild your carbs and learn a lot about the different circuits if you study the manual. (especially if you build 2 sets 2 or 3 times) Good luck and have fun with it.

cpotts454 · Posted: April 2, 2009, 7:16 am Post subject: Re: Carb Rebuild Opionon

My other concern is reliability. Like I said in previous post, I have rebuilt these carbs semi-successfully, I did loose a spring for the idle mixture screw and I did break the tube for the choke fill... So I pretty much have to buy a new set. I would have to assume that the new VM carbs has newer and more reliable technology. I have the same mentality as you guys, DYI where you can. The only thing I have paid to get done on this bike in the past 2 years was to get the the jugs bored. Carbs are just so feniky and problematic, I think its probably best to leave it to the guy that has years of experience.

BTW, I think I am sold on the VM carbs. More horsepower! Newer technology!

yamaman · Posted: April 2, 2009, 8:19 am Post subject: Re: Carb Rebuild Opionon

Mate, sorry to say, VM's have been around longer than XS's!
VM's are primarily made for 2 stroke engines, CV's simply wont work on a 2 stroke.
The beauty of VM's is their simplicity, their lack of technology actualy!
CV's definatly have their place & generaly make for a smoother running bike, the VM's are a harsher, more direct carb.

This should help:

72.14.235.132/custom?q...3607686099

Thats the html version, the slideshow is well worth the wait if you have a fast pc conection:

people.morrisville.edu...Theory.ppt

Mikesxs · Full Member Joined: Feb 06, 2007 Posts: 134 Location: FL

A couple of years of the Suzuki 750 2 stroke/3 cylinder (water Buffalo or Kettle ) used Mikuni CV carbs.

Mikes XS

yamaman · Posted: April 2, 2009, 9:33 am Post subject: Re: Carb Rebuild Opionon

Interesting, I never knew that!
I thought a 2 stroke would create less constant vaccum (probably wrong there too).
Perhaps the large capacity helps that out? Lighter springs?
I would think they would be far from ideal carbs, to many fluctuations between the pots? Or is this in its favour? Velocity would hardly be constant?
Any thoughts?

xs1961 · Posted: April 2, 2009, 10:54 am Post subject: Re: Carb Rebuild Opionon

I was always led to believe the same as you Yamaman..Maybe the power characteristics of the kettle make it unique, they always did feel more '4-strokey' in performance than a raggedy-arsed H-2/H-1 etc..

cpotts454 · Posted: April 2, 2009, 12:50 pm Post subject: Re: Carb Rebuild Opionon

Well I guess I was under the wrong impression. The Dellorto is the newer technology. None the less I went ahead and bought a set of new VMs from ebay. It says they are prejetted for the XS. I do have open pipes though, so I do not know how this will effect factory jetting. Someone chime in if they can. I have read several posts on this site about VMs but I most of it was jibberish because I dont actually understand the carb yet.

Thanks!

yamaman · Posted: April 2, 2009, 1:02 pm Post subject: Re: Carb Rebuild Opionon

Take the time to open the link for the slideshow I gave you above, well worth it!

ost of these settings are for open pipes or similar, should be a reasonable base line for you. Also download the Mikuni manual, the link for that is on this link, cheers:

650rider.com/index.php...pic&t=6268

xs1961 · Posted: April 2, 2009, 2:10 pm Post subject: Re: Carb Rebuild Opionon

Mine. 34mmm with Ramair pods, Triumph silencers ,Halco 1 1/2" pipes.
Pilot jet 25
Slide 2.0
Needle jet P6
Needle 6DH4
clip pos 3
ain jet 185 (190 some days)

cpotts454 · Posted: April 4, 2009, 3:50 pm Post subject: Re: Carb Rebuild Opionon

Due to a misunderstanding with one the description of the ebay item, I am left with no new round slides for the time being. I did purchase pamco petes ignition system and I plan on giving carb cleaning one more chance before I buy a $400 pair for 650 central.

I have two quick questions for all those who are listening:

1978 BS38 Carbs

1. I am missing the appropriate spring for the right side idle mixture screw. I am also missing, on both sides, the appropriate idle mixture screw o-ring. I am one of the unfortunate ones that have carb bodys that MikesXS doesnt have the right o-ring to fit. Does anyone know of a source that would have the spring and a right o-ring?

2. Also, I can't remember if I did this or a PO, but on the right side carb, the choke tube has been broke off and I cannot for the life of me figure out how to put it back on. Will this effect performance other then the choke function?

Thanks as always.

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Yamaha xs650