121 replies to this topic

[Blaqkfox]

Nope still rocking the mechanical fuel pump, from quantum, same one Im running on my other 3VD! Ill look into it this weekend and report back.

[Blaqkfox]

My fuel tank finally arrived!

https://i.imgur.com/t6zOAlg.jpeg

Its in pretty good shape! I wish I couldve found a perfect one, but this was the nicest one I could find. It has a slight dent forward of the fill cap, and a little paint chipping as well. Unfortunately its a little rusty too, not bad, definitely seen much much worse. Looks mostly surface but I do hear some loose rusty bits rattling around in there. I recon Ill give it the vinegar bath before I actually install it. Glad I kept all the old mounts and tap from the old tank, this one is completely stripped of all that.

https://i.imgur.com/QvIvEsd.jpeg

Honestly the dent is hardly noticeable. I thought it was funny that they actually sharpied it. I figured it was just done as a post edit to the photos on the ad lol

https://i.imgur.com/IKEqcAd.jpeg

Should come right off with a melamine sponge or whatever those mr clean magic erasers are made of.

It looks pretty good on the bike

https://i.imgur.com/Z0EEOXF.jpeg

For some reason I swear this 3VD sits lower than my other one. The forks are probably blown, but theres no fluid on them, perhaps its already all leaked out and been cleaned off lol. I have it a bounce the other day to confirm that suspicion, and it felt decent but not super stiff, tho I know these 90s Yamahas kinda have that spongy feel to them. Atleast that was my experience with my Seca 2 I had, and I rebuilt the forks on it and it was still soft. Ill have to bounce the good 3VD to compare, it just had the forks rebuilt last year and they feel great.

I also noticed this gas tank looks to be a darker red maybe? Did Germany get slightly different color red than we got in the states? Or maybe its just because the other tdm is directly under that spotlight in my shed.

https://i.imgur.com/s4Hh8Kq.jpeg

Edited by Blaqkfox, 20 March 2024 - 01:53 am.

[Catteeclan]

Has your other bike seen more sun, red fades big time.

[Blaqkfox]

She keeps fighting me but I am winning!

I found the left carburetor had a spec of debris in the float needle seat so thats why it was leaking. The right carb was a different story. I mustve taken that bowl off 10 times or more today. No matter what I did it would keep leaking.

https://i.imgur.com/qSH93zN.jpeg

The needle seat was clean and looked fine, the needle itself was brand new and looked fine, it wasnt binding, the o ring for the needle seat was new, as was the float which did float, and float pin. The only old piece was the plastic needle seat itself.

So I tested the float bowl drain tube, suspecting it may have a crack I couldnt see. With the bowl off, I filled it with fuel. It seemed fine, nothing happened.

Then I tested the system by turning the fuel on and manually holding the float down gently. Everything seemed to work just fine.

The only thing I could think was float height was wrong. But it looked to be correct compared to the old ones and the new one in the left carb. Regardless I decided to try it. No effect. No enough perhaps? Try again, this time with a drastic change to float height. At first I thought this had an effect. After as I was installing the battery it began to drip again.

This went on and on for some time.

Finally after a few hours and frustrated I replaced the o ring, sanded the surface it mates with, and tweaked float height again.

Finally it stopped. My float height is probably off by a few mm, but whatever. It seems to run fine.

With all that done I installed the gas tank. It was cleaner on the inside than I thought. It was cleaned by the person I bought it from, tho there was some surface rusting inside under the fuel cap, and I had to fish some loose rust out with a magnet. Installed the new fuel cap so everything works off 1 key. Installed the new fuel pump, petcock, and cleaned up the fuel tap on the tank. 3 filters and 14 hose clamps later it was all done.

I wanted to test ride it but it was getting late and I noticed the old rusty chain was too tight, and I only had a gallon of fuel on hand (I live in the countryside so for me to make a trip and back to even just the gas station is a 30 min ordeal).

So maybe next weekend I can finally get that first ride in.

https://i.imgur.com/YXLmNCv.jpeg

[Blaqkfox]

OH I almost fogot, once I had the bike back together I noticed something rather odd. The seat seems to have contorted itself…

https://i.imgur.com/lOjDMDt.jpeg

I think the fabric has dried out and shrunk causing it to pull the front and back of the seat inward, basically bending the seat. I can fit 3 fingers almost between the front of the seat and the fuel tank, and 1 finger in the rear between seat and the top of the tail fairing. Can’t say I’ve ever seen one do that before. I’m not sure how to fix it. I tried to see if I could push the front to where the Velcro would just hold it, and when I did I heard a pop and realized the fabric immediately ripped a large fissure from being so stiff and brittle. Shame, it was actually a good looking seat. Even with the fabric torn across the front from ear to ear I was still unable to fit the Velcro ends together. I recon it’s warped the plastic now too from being in that position so long. Guess I’ll just accept it the way it is or try some heat to bend the plastic atleast

[Blaqkfox]

FIRST TEST RIDE!

I couldn’t wait. I got home from work, lived the crap out of that old rusty chain, put some gas in it, and crossed my fingers. Fired up and all seemed well. I checked the chain after I lived it and it seemed to have a more proper amount of play now.

Put in gear for the first time and immediately stalled it lol. The clutch plates were stuck of course. About 10 burnouts and stalls later I finally got them to start to free up. I still had to gas it and dump it to take off out of the driveway. What a thrill.

I rode around for maybe 20 min at most. I wanted to get it warm enough to burn off any old moisture, but I probably did already when I was balancing carbs and everything else anyhow.

For the most part the ride was great! But there was one bothersome thing…

Every couple of minutes there was a jarring jolt from the bike, almost like a fuel or ignition cut would feel. Honestly, I don’t want to jinx myself here, but it felt like the engine was trying to lock up. I mean it ran fine otherwise and it was only a split second this would happen. I do think it’s fuel delivery related tho, I could never tell exactly when it was going to do this, but it tended to happen in 1st-3rd gears, at about 1/4 or more throttle. I would just be cruising along and it’s like someone flipped the kill switch real fast, stumble but then perfectly fine the next second. I did discover I could duplicated this issue on command, as any quick throttle input would result in it happening.

Was it the chain binding up? Was it a fuel issue? Spark? Engine knock? Clutch related maybe? Or maybe it does need a valve adjustment, it is hard to start after all, but it’s not even due for its first one for another 10k miles. I really don’t have a clue. I double checked when I returned and fuel was viable in the filter, fuel was topped up plenty. Perhaps a carb related fuel issue. I did have all that trouble with the right carb after all.

My front brakes were also still really spongy but they worked. Same with the rear but worse, it’s not really usable atm. The speedometer does not work, and I know it’s the gsuge itself that’s broke. And I can’t decide if the forks warrant a rebuild or not. They feel almost as stiff as my other tdm but they sit lower. But what a fun first ride! I really want to know what that jarring was tho.

[fixitsan]

My mk1 would give an occasional cough like that too. Never found out the cause, and it never caused a problem

Well done with all the work so far

[Blaqkfox]

Thanks. I can only think of two reasons for a little backfire out the intake. Either the intake valve isnt closed when it should be, or spark timing. But this isnt a points equipped bike so its likely not spark timing. Which makes me think something is up with valves. Be it the timing chain has stretched, or maybe the valve isnt seating fully, which could likely be due to needing a valve adjustment. These are bucket under shim so they will tighten up as they wear which can hold the valve open. Being it runs as well as it does once its warm but can be hard to start cold, I believe thats the most likely culprit. Ill have to check.

[fixitsan]

Thanks. I can only think of two reasons for a little backfire out the intake. Either the intake valve isnt closed when it should be, or spark timing. But this isnt a points equipped bike so its likely not spark timing. Which makes me think something is up with valves. Be it the timing chain has stretched, or maybe the valve isnt seating fully, which could likely be due to needing a valve adjustment. These are bucket under shim so they will tighten up as they wear which can hold the valve open. Being it runs as well as it does once its warm but can be hard to start cold, I believe thats the most likely culprit. Ill have to check.

You can get a little intake blip like that with an lean mixture, as if there was an air leak via the intake rubbers. A MK2 I had would do it now and then, The rubbers looked good, but once the carbs were off and the walls of the rubbers were flexed they put up a lot of resistance and a few cracks became obvious. I was hard up in those days, so covered the outer wall with silicone !

[Blaqkfox]

Oh I see, well that wouldnt be my issue, mine are new rubbers. Appreciate the info tho

[Tedious93]

Been reading this thread with some interest as I have been resurrecting my own '93 which lay fallow for some 12 years. About the only thing that happened over that time was I'd fire it up now and then to see if it was still ok (when the battery was charged of course). I've seen all the usual symptoms so can relate but as to fuel cutoff I'd go back to the that tank (check the filters and the flow on main and reseerve) and down through the fuel system (pinched lines?) to the inlet to the carbs where there is a very small filter installed inside the plastic "T" fitting. The other thought was your fuel level may be to low and/or pump doesn't meet demand or messed up. Make sure you've got at least a couple gallons in the tankI switched to one of those electric pumps and the thing starts well after letting it fill the bowls upon Key ON.

 

For others who may be rebuilding the Mikuni BDST 38 found on the 850 bikes I found this video useful though it's for an FZR1000.

 

https://www.youtube....h?v=jiwHfbCTLMc Part 1

 Part 2 https://www.youtube....h?v=Jm_ZIcgb2xY

[Blaqkfox]

Welcome Tedious,

Appreciate your knowledge! think the problem lies in float height, only trouble is if the float is any lower if causes the bowl to substantially overflow. But its obviously way out of spec. Like 10mm out of spec. Ive tried swapping needles around but that didnt work.

the tank is new, I cleaned the old fuel tap that bolts on the tank and reused it, the filter wasnt in great shape, but I put quality in line filters on both the lines from the tank to the new petcock, and then theres another filter from the petcock to the new fuel pump, and one more from the fuel pump to the carburetors just to be extra extra extra sure. So all thats brand new parts- the petcock, pump, lines and filters. And the tank wasnt the cleanest with some rust but I think I got most of it out.

Also the carbs themselves have had a full work up- fully separated and sonic cleaned, new gaskets, new floats, float needles, etc. only the original emulsion tubes, plastic float seat, and plastic slide inserts remained. Although I dont remember seeing a filter in the T fuel fitting on the carbs. Dont recall my other tdm having it either. Im sure Im not the first one in here though. But Ive checked the bowl overflow spout isnt cracked causing the leak, Ive tested the float and it floats and not fuel logged. I do wonder if the float seat could be the culprit. It looks perfectly fine but maybe the plastic has an imperfection or deformity I cant see. I think Ill try swapping them next and see if the problem follows.

Or maybe pinched lines but I doubt it. The fuel cut I think only exist on one cylinder. But Im not sure.

Unfortunately I havent had much time to devote to it lately. Just finished a cafe kz550 my buddy wanted me to build for him and taught him how to clean the carburetors on his cm400t hes bought for our budget build challenge. And Ive spent so much time in the shop lately I need to make time for the wife and all, so Im taking this weekend off to spend with family. Then my buddy is bringing his vintage 125ks2 Kawasaki to me next weekend so I can rebuild the top end and diagnose a no spark issue on it, as well Ive got a carb rebuild lined up as side work on a zx6r. So its probably going to be another three weekends before I can get back to the tdm. Which just leaves 4 weekends until our trip so Im gonna be scrambling to get this issue sorted and get the chain, tires, and fairings put back on so itll be ready for the trip.

Edited by Blaqkfox, 12 April 2024 - 04:39 am.

[Snowbird]

What fuel hoses did you use? On my 4TX Mk2a I fitted a fuel tap off the Mk2 so I could run the carbs dry for winter and found it would lose power after a blast of flat out but come back after a bit of slow running, changed the pipes back to original and all fine, the original pipes are shaped and thin walled but regular pipe off a roll didn't like the tight turns required.

Some time I will have another go at plumbing up the tap but need thinner bore pipe, I was working on the idea of leaving reserve spigot open so it could suck in air for the last mile ridden and leave the bowls nearly dry by the time I got home so it could just idle till it died.

[Tedious93]

As a check, remove the fuel line to the carbs and check for the small filter that fits just inside the inlet of the "T" fitting. If you have confidence in your other in-line filters, just you can likely get away without it if it's messed up and you're sure the line is debris free. It may be the fuel pump is deteriorating or introducing junk into the line.

 

What type of fuel pump did you say you were using? If you have the old vacuum pump, throw it in the trash.They are the cause of flat spots at mid range and hard starting; all due to inadequate fuel supply. Get an electric pump (preferably an early FZ, FZR, R1). Note that the Chinese pumps on Amazon and Ebay have large diameter pipes that don't fit the stock size fuel lines. Since there's no plug for an electrical pump wire it into the hot side of Starter Cutoff relay and the ground of the Flasher relay nearby. That hot line is fused going to the ignition switch so it's safe and will operate the pump at Key ON filling the bowls before you hit the starter button. The pump will also shut down with the kill button like it should.

CAUTION! DO NOT WIRE IT TO THE BATTERY OR ANY LINE IN FRONT OF THE IGNITION SWITCH! Consult the schematic in the service manual.

[Studley Ramrod]

Hi, sorry, havent read all the posts, suffoce to say. Have a good look at the float bowl. If the drain screw is overtightened it can crack the bowl and give the impression that it's overflowing. The crack might not show itself until the drain screw is tightened up.

[dapleb]

I disagrozzle with the electric pamp comment. NEVER fit any extra electricity to a MK1. The orig pamp is mega reliable and simple. If ewe have flat spots then replace the arseytate.

[Tedious93]

IF I filled my tank every time before I put the bike away and IF I never let it sit for more than a week and IF I had never needed full throttle when my fuel level/jetting was set a tad low (lean) you're right. The vacuum pump is adequate. I suppose it's small enough to carry as a back-up. I've never heard of Yamaha pump failing. Lucas? Definitely.

 

With regard to overflowing float bowl, I agree about the drain screw. Too, it may not be the needle or the seat but the O-ring around it could be perished(hard).

 

At the risk of debate on fuel level, float height which determines fuel level is critical (especially so with a vacuum pump). Depending on the jetting most fall between 12 and14 mm above the gasket surface when the needle just sits on the seat by gravity. Most important is to bolt an edge of the bowl over the seat/O-ring assy. to hold it down before taking the measurement. While the service manual specs fuel level; using float level often gets you there with less iterations of adjustment/work. Remember Higher float = lower fuel level. BTW, I've found that the electric pump is more forgiving about fuel level but of necessity you MUST have a float/needle/seat all in good order.

[dapleb]

Also note, float height should be measured on the rectangular float (rather than the diamond one) as there is a few mm diff in height of the two floats!

[Blaqkfox]

Yeah everyone says that about the mechanical fuel pump, but my other tdm is running the same quantum brand pump I put on this one, and it works just fine. No flat spots, no weirdness. This tdm had an electric pump that I was given with it, guess that explains the wire I was asking about earlier that was coming off the cut off relay. The cut off relay on this one was burned upwonder if it was due to that electric pump conversion

Edited by Blaqkfox, 14 April 2024 - 12:45 pm.

[Tedious93]

I doubt it. Most of these pumps draw very low amps (<2?). From your description of the "interesting" history in the electrics I'd bet it was something else but obviously I don't know how the pump was wired in. As you have described folks get desperate when electrics don't work and patience takes a holiday; let alone attention to detail.

 

Took a look at your vids on Tic Tok ... couldn't see the topic bike of this thread but you're other TDM looks handsome (even if you did drop it)

Dropped mine years back (front brake on wet grass) ... nothing but grass stains and a divot or two ... so lucky.

 

Don't recall anything about the rebuild of the carbs. Is everything stock? 140 main? 5EL79 needle?, Y4 emulsion tube? 37.5 pilot? screws 3T out?

 

As for my resurrection, it's coming along. The carbs go back on the bike today. My tank needs attention too so I'm running a fuel bottle and hooking a battery externally so I can get at the fuel screws and sync the carbs (assuming it starts and runs decent.)  ... Onward!