March 2010 45

Hello there !

Just bought a 1984 Suzuki GS750E and has an issue starting if its cold the person I bought it off of told me to cover the air box for a second while trying to turn it over, then remove it then start it again. Any clue why its having a hard time to start in the cold. As well when I looked in the air box I noticed it didnt have a air filter could this be an issue with my problem? any help would be greatly appreciatied. Thanks again

Jay,
Jasper Ab
Canada

Missing an air filter can DEFINITELY be your problem. Some bikes are extremely sensitive to the air/fuel mixture, and when the airbox is opened up the bike is getting way too much air in relation to the amount of fuel entering the cylinder.

First thing I would do if I was you is put in a fresh air filter. I wouldn’t be surprised if it completely cured your problem.

Cheers Jay!

I had 4 XS650’s over the last 35 yrs so I can appreciate your sentiments but that is not why I am writing.

I just modified my XV1100 SH (1996) Virago to accept a H-D K&N RK-380B air cleaner assembly. I am thrilled w/ the modification and my OEM jetted carbs are great from idle to 3/4 throttle. After that the bike feels as if it has a miss. I believe that I have to replace the main jets. Another Virago tech forum member did a similar but not identical mod and had to open his main jets two sizes larger. My Hitachi HSC40’s have stock sizes of, Front #122, Rear #128. Does that mean that I should go, Front #126, Rear #132 ? I appreciate your advice.

Your jet size estimates sound correct. When you change an intake or an exhaust you’ll generally go up on the main jet anywhere from 1 to 3 sizes. 2 is probably about right for your bike, but personally I never make jetting adjustments in increments more than one jet size. If I was you I would pick up a 124, 126, 130, and a 132. I’d go up one size on the main jets then give it a ride. If it still stammered at open throttle I’d go up one more size.

Most (imported) transversely mounted air-cooled V-twins like your Virago run the rear cylinder richer than the front to keep it cooler because it doesn’t get a whole lot of air flow. Kind of an interesting solution to a specific problem. Just part of the reason the big twins never have a competitive edge in any racing circuits.

Anyway, thanks for reading the blog. Let me know how it goes.

Lots has happened since the message below.

1- It turns out that the Factory service manual was wrong.  I do not have Hitachi’s I have Mikuni’s.  This is very good because of widespread availability of various jet sizes.

2-  After becoming extremely effective and proficient at removing and installing carburetors I have finalized the jetting.  140 for the front cylinder and 137.5 for the rear, that’s 6 sizes up.  I opened the pilot jets up to 42.5, that’s one size.  If you read your attached post you can be amused that you threw me one.  I thought that my jets were in ass-backward but after I inquired on the Virago Tech Forum  I found that not to be the case.  I was severely chastised.  The front cylinder is richer of the two.

3- My Photobucket slide show is complete.  Here’s the link http://s156.photobucket.com/albums/t23/ … 20Cleaner/
Please view it and provide me w/ some honest critique.

4- I synced the carbs w/ a homemade “Manometer” constructed for <$4.00.

That’s it.  If anyone can use any of this info then pass it on.

Great looking bike you have there.

I find it very odd that the front cylinder would be the richer of the two. I’m going to do a little reading on that out of curiosity, I can’t think of why that would be. Glad you got it sorted!

Hey, great blog! I love checking out your updates and the nice work you do. I’m in the process of purchasing my first bike-1980 Honda CB650 and wanted your opinion. The original owners still have the bike and it’s only got 3,800 miles on it. They are in their 80’s and want the thing gone. Because it sat for so long they took it to a friend/mechanic and got the tank sand blasted and sealed. I drove the bike around and it runs decent but needed the choke. They are willing to give it up for $700. This is by far the best deal i’ve found but figured i’d get an experts advice? Also, what’s a good place to get parts for a bike like this, preferably online since i live in the boondocks of Indiana.

CB650 SOHC’s are great bikes. They are a good mix of comfort, power, and ease of maintenance.

Any bike that has been sitting that long will need a thorough carb cleaning – it’s not hard to do, you can read my how-to article on the site.

Just as a word of advice – only buy a bike which has sat unused if you plan to learn about motorcycle maintenance. Bikes that have been sitting should always get a proper lube and inspection before putting any serious miles on them. The bike will also needs tires, etc. If it’s in real good cosmetic condition $700 seems OK, but not great.

My one word of caution would be – old bikes that have sat idle have dry rubber – inspect the seal around the output shaft of the motor (behind the front sprocket).  If that seal leaks the bike is basically worthless, because the motor has to be completely disassembled to replace it.

Good luck with the new ride.

Peace and grease,
-Evan

I recently purchases a maxim 550. I was told by the previous owner when I got it that the only thing it needed was the carbs cleaned. I found your page on cleaning carbs but I really don’t know what I’m doing. One question. I took everything apart (not each carb from the set but all the little screws and such from inside like in your page) As I was putting it back together I wonder if some of the screws are supposed to be set a certain way. I mean, do I screw everything back in all the way? there were a couple that looked like they could be for adjusting.

All the internal jets will seat all the way in. Screw them all the way in, and apply gentle pressure to seat them – DO NOT crank on the jets or twist strongly on them, you’ll strip the brass. Just a light seat is all they need.

The only ‘adjustable’ jet you may be referring to is the air jet, which is installed and adjusted from outside of the carburetors. This jet is long and pointy. A general rule of thumb is about 1.5 turns out from seated. So screw the jet in all the way (gently!) – once seated turn it back out 1.5 turns. This can be adjusted up and down depending on the bike, tuning, elevation, etc.

I recently bought a 1972 Honda CB500 for 400 bucks and I plan on turning it into a cafe racer. This is my first bike ever and I’ve done a fair bit of research into the bike, but I’m still trying to figure out which parts I can swap from other models such as the 550 or 750. Specifically things like the front forks/triple clamp, exhaust, seat, rims, etc.

I know some websites list which parts will fit which model of bike or have universal parts, but some sites I’ve looked at only refer to the 750. Perhaps you can clarify if these models have inter-changeble parts or maybe send me in the direction of a good source of information.

Thanks for your help and guiding newbies such as myself. Oh and I really dig the blog, keep up the good work.

The Honda CB500 (four cylinder) shares the same size forks as the Honda CB750’s. They are all 35mm forks.

35 Honda CB-500 “500 Four” (71-73)
35 Honda CX-500C “Custom” (81-82)
35 Honda GB-500 (89-90)
35 Honda GL-500/I (81-82)
35 Honda XL-500S (79-80 To 5104835)
35 Honda XL-500S (80- 81)
35 Honda CB-550 “550 Four K” (74-78)
35 Honda CB-650 (79-80)
35 Honda CB-650 (81-82)
35 Honda CB-650C (80 To 2009951)
35 Honda CB-750K (69)
35 Honda CB-750 “750 Four” (70, 72)
35 Honda CB-750A “750 Hondamatic” (76-78)
35 Honda CB-750C “Custom” (80-82)
35 Honda CB-750F “Super Sport” (75-78)
35 Honda CB-750F (79-80)
35 Honda CBX (79-80)

Exhaust and seat will be no-gos, but if you are doing a custom cafe project you’ll want to use something aftermarket/home-brewed anyway.

The guys over on the SOHC4 forum can help out with specific part interchangeability, but CB500 parts are not hard to come by so you shouldn’t be wanting for too much.

First things first, great site. Appreciate your willingness to share your knowledge. I live in West Newton, MA and am getting ready to restore a ’77 Honda CB400F2. I am looking for someone who can lace and true the spoke wheels on the front and back. I am going to be using the original hubs, but have bought new rims and spokes as the originals are severely rusted. Can you point me in the direction of someone who knows how to do this work?

As someone who prides myself on doing my own work, I must encourage you to tackle this project on your own.

It will take a beginner a few hours to lace a true a wheel, but it is not an excruciating task. Take photos of your wheels so you can note the pattern. Tear them down (I would take a grinder to the spokes and cut them out). Then re-lace one spoke at a time. There are lots of great how-to’s around for this, and I may even put one together in the near future.

As for truing, a simple homebuilt stand can work just fine. Or a simple balancing/truing stand from a vendor like http://www.beemerbalancers.com (I am affiliated with this company FYI) will work fantastically. I use the pocket balancer and it works great. You’ll want to double check your bearing size though because I can’t remember specifically what the CB400’s use and they only offer adapters to fit certain sizes.

I read your article about cleaning carbs with boiling lemon juice.

I’m so glad to know that as I have used the useless spray carb cleaner and it does not do anything except make my fingers crack open!

I have a KZ 650 and 77 Kz100 LTD I need to do the carbs on.

Well, I wouldn’t go so far as to say that spray carb cleaner is worthless. It certainly has it’s place, and I use it pretty much every time I dig into carbs. It’s great for cleaning up slides, throttle plates, and wiping out bowls. But if your carbs are real gummed up spray cleaner isn’t the easiest solution. You’re better off with a more harsh carb dip. And/or boiling.