xj750 Maxim: low acceleration after rebuilding carbs

I bought this xj about 3 months ago. I knew it would have some work, but nothing I thought I couldn't handle. Started out by replacing the fuse block to the blade stylie. It has been sitting for several years and had some rust develop in the tank, so I removed the tank and applied POR15, rebuilt the petcock, and brass brushed off the rust from the fuel sending unit to "Clean" them up. I then removed the carb's and rebuilt them. I did not take them apart, I cleaned them good by disassembling, soaking, then installing new needles and seats, along with a few other parts that came along with the rebuilt kit. I bought and installed a new battery. Reassembled and was able to get it running again. Smooth, good throttle response. felt pretty good. Drove it around town for about a month, During this time I also replaced the battery low water sensor with the relay stylie, and rebuilt the starter. Then the throttle response started getting worse and worse. After further investigation I discovered rust particles in the fuel filter. (!@#$). I don't like doing things twice. So I removed the fuel system again, and cleaned everything up, again, bought a new fuel filter, and new in-tank filter. got it all reassembled again yesterday. First the throttle response was the same, but after a few revs something clicked and the throtle response was good. I am thinking, one of the needles must have still had something in there. I then test drove around the yard and I could only get it to drive enough around the yard, with no real acceleration and I also noticed some back firing, but not super noise to wake up the neighbors, but enough to notice but still chug along. I would say my technical knowledge is about middle of the road, but with some help think I can tackle this. If you have other posts that relate to my prob just point me in that direction and I'll see what I can do. Thanks in advanced. zh

 

Hi Zach, welcome to the camp.
Backfiring or popping on deceleration is often associated with a lean running condition. A lean condition can come from several different conditions.

Given what you described, I vote that you remove your carbs, 'break the rack' and do a full rebuild, including replacing the throttle shaft seals. We call it Church Clean here.
http://xjbikes.com/forums/threads/in-the-church-of-clean.14692/

Once the rack is done proper and tuned and synched on the bike, then if the poor running condition persists we can troubleshoot other areas.

 

Have you also done the valves?
Gas tank cap vent may be rusty as well

 

Soaking the carbs without full disassembly will have damaged the throttle shaft seals. They must be replaced. Follow Stumplifter's advice, thn we can move on to Toomanybike's advice.

You will also need to set the float height since you replaced the needles and seats with new.
Setting the fuel levels

What rebuild kits did you buy? There are a few out there that have parts in them that aren't quite correct for the machine.

 

Doesn't soaking the carbs jeopardize damaging the diaphragms as well?

 

We hope he removed them and the mixture screw blind plugs as well

 

Sorry, original post was so long, I glossed over

I just caught the

and off I went.

 

Zach,

Please elaborate on your cleaning process....so that we can help you more.....you need to be more definitive when discussing repair & cleaning processes......

 

They should be like this !! And all the rubber bit look like this 99% of the time

 

2many,

Nice organizational skills.......looks nice

 

You most likely have ruined you shaft seals this will lead to vacuum leak. From your decription your synch is off popping is one symptom this means one or more carbs pulls more than another. ^^^^^+1 on what all above have stated .

 

Here's what I gather from the description of the cleaning process:

means they didn't break down the rack, and

means removing the bowls and hats and all the goodies inside. Until op clarifies, that's what I'm going with. Somebody still needs to be shown the way to church.

 

When you have it Set up like that, much easier to reassemble
And you know if anything went missing

 

I don't see your springs for your enrichment plungers...just an observation.....

 

Only the brass bits go into magic solution

 

Been trying to reply to posts since yesterday but keep getting the dreaded Spam message, so I removed everything I typed and started over. hopefully this helps. I'll get to answering the questions later today. Thanks for everyone's help so far, zh

 

OK, so looks like I can reply now, or I know what i'm doing, that's scary!

I bought a carb rebuild kit off E-bay. It did not include any Throttle Seals. kept the linkages together did not break the rack. So the throttle seals did not get replaced.

Valves have not been done, nor have I cleaned up with Tank filler cap. However when I test drove it the second time, I left the cap open.

Forgot to mention in original post, I did replace Oil and filter, so that is all new and clean.

Not using POD type filters, I'm and original type guy.

Diaphragms were removed before soaking.

Mixture screw blind plugs as well, If they are blind then then didn't get removed. No I think those were missed in the first and second cleaning.

@Toomanybikes - Very nice looking carbs and agree very well organized.

@Stumplifter - From what everyone is describing it looks like my next step is to go in-the-church-of-clean.14692 and follow step by step instructions.

Thanks for the excellent advice. I'll let ya know how it turns out. Thanks again! zh

 

Zachary - ask more questions if you need help.
Otherwise a digital camera, notes and patience will make easy work of Church.

Oh for heaven's sake - put on your nice pants!

 

@Stumplifter, @Toomanybikes @MattiThundrrr @Jetfixer @k-moe I am now backed up on basement home remodel project for the next few months. The Mixture screw blind plugs and Throttle shaft seals are going to have to wait, unless you know anyone that I can send these off to and rebuild for me. I tried locally, but not getting a response. as for adjusting values, shouldn't take much. bike only has 9,000 miles and when I had it running after the first rebuild, it was running very well.

 

You can send them to @hogfiddles or to @Toomanybikes for total overhaul.
Shipping cost would be the same as my parts shipments go to Washington state

 

Toomany has been bragging lately about how clean he gets carbs with vapor blasting or something like that. I've seen pictures, they sparkle. Hogfiddles is legendary, better than new. He hosts the carb event of the year! Either way, you will not be disappointed.

 

Yea Matti I've been getting sore lips from blowing my horn

 

My seals went as well

Just got my carbs back from hogfiddles and more than pleased

Really need a full rebuild

 

Must. Not. Comment!