2000 Yamaha Big Bear 400 No Spark Mikuni Carburetor Install (Continuation of No Spark)

**Gwbarm** · April 22

I got my no spark issue sorted out, got it running on the old aftermarket carb, but it didn't want to take throttle even after cleaned it, didnt really want to waste time on it, so I order a new one which is on its way, so not much to post here, but I wanted to start a new thread. I am stating to clean up the plastics thought I might as well do that while they are off, they were a mess tree sap, bird dropping, mold and what ever. Washed them good and got all off so I could see the oxidation , decided to wetsand with 600 grit waterproof sandpaper, and used Armour All instead of water. I figured it could put some of the moisture back in that was lost from sun exposure.

Working fairly well I will keep going finer on the grit and see if it will polish

**Gwbarm** · April 23

I decided the exhaust needed a little attention while it was all apart, very rusty, surprisingly i got them all off except 1, the one closest to the exhaust outlet that holds a heat shield in place, the head on the bolt was not even 10mm anymore, I didn't push it because if that one breaks its the only one holding that part of the heat shield in place and I probably would not be able to get the stud out. I would like to, just to clean the rust out, might keep trying but its there. Its always a challenge getting 25 year old exhaust bolts out. I tried cleaning it without taking it apart, but I could only imagine how much mud and rust was on the muffler, don't really want that to rust out.

The 14mm that holds the muffler to the frame were stubborn and needed a little persuasion to come out, of course all the original metal was covered in rust, I will just get the rust off and repaint with high temperature paint.

**Gwbarm** · April 25

Got the exhaust all delisted and back together, ran out of black high heat paint so I found some red engine enamel probably not my choice but its what I had, may change it later.

Still working on the plastics they cleaned up very well but they have had a rough life had one crack that I repaired and a lot of spots where the plastic had been flexed and its a lighter color there only way to hide that is paint and I don't really like to paint plastics, I have wet sanded from 220 to 5000 grit and they will polish nicely, still not decided what im going to do. The carb will be in tomorrow so I forget this for a while, but I will have to put the back plastic on to fit a seat to see if it drives.

You can see the areas im talking about lower right, middle right and upper left. Oh and don't laugh at my mobile work table, there is an interesting story behind that.

**Gwbarm** · April 26

Got my carbs in an OEM, and an aftermarket, I have a few side by side photos, just for fun can you choose which one is the Mikuni:

Saskatchewaner · April 26

On 4/24/2023 at 8:44 PM, Gwbarm said:

Oh and don't laugh at my mobile work table, there is an interesting story behind that.

Not laughing, what's the story?

**Gwbarm** · April 27

My wife decided instead of working on my heard of 4 wheelers and motorcycles I should put my services to better use and install a granite countertop in the kitchen. I found some she liked at a local building supply salvage store cheap, but they didn't deliver. I had help loading them in my navigator, but when I got home I had no help, I wouldn't ask anyone for help , if they hurt themselves I would feel bad and I know my limits, this job exceeded them greatly, so I had to figure out a way to increase my limitations. I had a few 8 foot tables and I slide them out of the back of the truck fairly easily onto the tables, them started to fabricate, cutout for cooktop and sink, that is where the rolling worktable came in to play. After the cutouts the granite is weak and will crack plus I can't lift an 8 ft piece by myself. I needed a way to get them in the house. I built this frame inside of a little garden trailer the same height as the cabinet so I could roll it up to the cabinet and slide it off with out stressing the weakened granite, granite is not plug and play. The little rolling work table worked so well I just left it together and use it for lots of projects. Now you can laugh!!!!

**Gwbarm** · April 27

No guesses! Its the one on the left. It is kind of foolish wasting this much brain power on a carb, I should just get the cheapest one stick it on there and go, been there done that didn't go very far, after going to this much trouble I do want it right.

**Gwbarm** · April 29

I did notice a few differences between the OEM and aftermarket carbs:

The throttle return spring was stronger

The idle adjusting cable was larger

The mixture adjusting screw was covered up with brass plug

The choke plunger was made out of aluminum with an O ring and a little longer with a different shape, and stronger spring

I didn't take it apart and compare the internal im sure there are more differences there. Since most aftermarkets don't have jet sizes on the jets hard to compare without a measuring tool I don't have.

**Gwbarm** · April 30

Started trying to get this Big Bear back together so I can see how it drives:

Put the new carburetor on

Worked out very well now instead of the throttle cable adjustment being adjusted out to the max it fits just right.

Still had an air box hose missing tried to order one listed as not shipping no aftermarket available, not suprized, so I have to fabricate one

It fit in the tank cutout well, just need to cut it off flush, and it just appears to be open under the seat not hooked to anything

**Gwbarm** · May 1

Trying to get the wiring sorted out and routed back in its right places, a little brain teasing when you didn't take it apart.

Test fitted the back fenders to try to figure out which wires went through which hole

Got it all wired up after repairing some of the broken wire hangers.Everything fit where it was supposed to go.

Went to screw it down and found this , broken off bolt down in a hole, iv got it soaking with PB Blaster now, not sure how im going to get this one out yet, it may be difficult. So I had to take everything back apart to get to it, not to bad, I had already done the hardest part, figuring out where everything goes.

**Mech** · May 1

Grease all those bolts Gw..

Looking good mate.. nice tidy job.

I'd be a bit watchful when it's going that that rubber hose isn't a bit restrictive.. Might pay to check the carb first without that hose on there..

**Gwbarm** · May 1

Thanks Mech! I have been putting Anti Seize on all the bolts as I go in with new hardware, I tried to get the hose routed as close as possible to the original , which was missing, the parts house I generally use doesnt stock the original anymore, im still looking, expensive hose 115.00, I still need to cut it off flush with the tank, but I will try running without it as you suggested. I was just trying to get the air box hooked back up before I start it, sometimes they can run too lean without air box attached.

**Mech** · May 2

Yup, need the box and filter before passing judgment on the new carb.

**Gwbarm** · May 2

Well it turns out that the broken bolt was in an insert into the frame. It broke loose as I was trying to get the bolt out. I tried to get a new one but yamaha doesnt even list it as a part.

So I went to Ace hardware thinking they may have something to replace it, nothing metal just some plastic inserts. I ended up using a license plate mounting insert, it fit the hole perfectly. I would like to replace it with what was there, but I think this will work.

Got the rear fender mounted now, and all the electronics routed to their correct place.

**Gwbarm** · May 5

I was going to start it up with my new carb today , and forgot I had mowed up all my non ethanol gas. The station where I get it was across town so I didn't get to do that. So I thought I would work on the plastics some more. The front I had worked on last week, I had wet sanded all the way up to 5000 grit and polished it, looked good, but being out in the weather a few days the oxidation came right back.

So I figured that would not work so I sprayed it with clear engine enamel. I liked the look of it it, gave the blah beige a little deeper warmer tone. Did a test fit and its starting to look like a Big Bear again. I sprayed it a little dry I wasn't sure if I wanted a high gloss, I can polish it later if I change my mind.

These are the stress spots that were discolored, don't bother me to bad yet, I thought I would try this first, not much I can do for that except paint.

**Gwbarm** · May 6

I found another broken bolt on one of the racks as I was fitting everything back together. I worked on it a couple of hours, wasn't budging, like it was welded there. I had to drill this one out and rethread it.

On this project I received it all apart, and no bolts to put it back together. Looking at OEM bolts ranging from 4.00 to 8.00 per bolt, I new that wasn't going to happen. I found these stainless steel flange head bolts, and pan head screws on Amazon reasonably priced, I am very impressed with the quality, it is the hardest bolt I have ever tried to cut and heavy. Just wanted to share if anyone is needing bolts orinterested.

**Mech** · May 6

I go see the local wrecker every few years Gw and buy a wooden nail box or wooden box full of assorted bolts for twenty bucks.. or less. They are generally happy to get rid of a whole box full for more than scrap prices.

I could sell you a box full of the real strange bolts that never get used.. real cheap..

**Gwbarm** · May 7

Thanks for the offer Mech, It sounds like you have a good deal with the wrecker, I think im good, plus shipping over 3 ponds might get quite expensive. I may have exaggerated when I said it was all apart, coil bolts missing, cdi bolts missing, tank bolts, all of the plastics and rack bolts missing. Suspension was all together, engine was all together, but side cover had several missing, but I found them, they were holding the stator in place, replaced them with the pan head screws it was supposed to have. I may find more missing as I continue putting it all back together, but so far they have all been 6mm.

**Gwbarm** · May 11

I ordered a few of OEM bolts that I felt were specialty bolts, the ones for the engine case and stator mounting bolts, I will have to say at 4 and 8 per bolt I was not impressed at all, more impressed with my stainless steel amazon bolts, 25 for 10.00 which would have worked fine, the one for the engine case that was broken, the original, was nice stainless, my replacement was black painted, the others were just pot metal. My conclusion is replacement OEM bolts are a big rip off.

**Mech** · May 12

OEM bolts are good quality, but yeah overpriced for sure from the dealer.

On jap quads the bolts are chosen for a variety of properties though, some are really tough and/or have washered heads, and some are rust resist, and some are soft so they can be drilled out easily. Some have small heads for their size. Then there are the bolts with fattened shanks made to go through rubber grommets or plastics without crushing the plastic. All those sorts of bolts are used on jap cars as well, which is why the big box of bolts from the wreckers is so good.. There's always the special bolt you need in there. My local wreckers throw bigger bolts and smaller bolts(and nuts), into separate boxes. They're happy if they get scrap steel price for the box.. I give them more. Big boxes of nuts and bolts are good to have.. People come here for bolts because they are so dear to buy from the engineers or OEM. The best thing for me as a mechanic though is being able to grab the right spec bolt for the job when I need it without having to ordering that special "part" form the dealer.

**Gwbarm** · May 17

Finally got back around to the Big Bear, between all the rain and other priorities time has been limited, I keep up three properties so the John Deere has been getting a good workout, got the new Mikuni installed all the hoses routed where they are supposed to go, that took a minute, put in new fuel gauge, the other one wasn't even there , it must have rotted off and fell in the tank, so previous owner removed it. Buttoned up a few more loose ends and started it. I will have to say im very impressed with the new Mikuni glad I found one cheap enough to buy on Ebay. I learned the hard way , but I do believe in OEM carbs, I may scrimp on other aftermarket stuff, but wont on Carbs anymore. Oh, one other thing, when you buy an aftermarket petcock pay attention to the nipple size, even when the add says it fits 2000 Yamaha Big Bear, and don't get one smaller than your carb nipple, ask me how I know.

This video is the first start with the new carb:

It takes throttle very well and smoothly without stumbling a tad, which I what I would always get with Aftermarket. This video is after its been running for a while, no smoke, but the engine sounds a little pingy, im going to pull the valve caps to make sure its oiling correctly, but this is my first Yamaha it might be a normal sound for them, what do you guys think.

**Gwbarm** · May 20

I did start the big bear again today, it start so easily with the right carb on it, engine sounds a little rattly to me but no smoke whatsoever ever, it does go away when I rev it up, I haven't checked the idle speed yet it may need to be idled up, but it sounds good to me where it is, and if you noticed I have a little leak from the stator cover, I was expecting it, aftermarket gasket didn't fit it exactly right, got a new OEM one , just got to get it installed.

**Gwbarm** · May 23

I changed, the leaky gasket and oil on the Big Bear today, I put this Shell Rotella in about 2 months ago after I got the engine unstuck with very little milky looking oil in it, still looks like muddy water, and I have run it very little. I cranked it with the new oil and it runs very well and the gears all work so that is a plus. I wasn't sure if the clutches might be stuck as well. Going to run this oil a little bit and drain it as well along with changing the filter again.

**Mech** · May 24

Eek ! That's nasty Gw.. Better out than in.

They must hold a bit hidden in the oil cooler and places huh..

Glad to hear it's running great, and it looks good too mate.. well done.

**Mech** · May 24

Regarding the noises.. You can deduce a lot by taking note of the circumstances when it makes noises, like under load only, or not under load but only when floating, or both, and whether it's better or worse when cold, or hot, or always there, and how long the noise lasts from cold if that is the case. It's good to try all the load tests while it's cold and then when it's hot. It's harder to do on quads with centrifugal clutches but on manual clutches you can tell if it's gearbox by pulling the clutch, and you can load them up o the spot using the clutch, which is way better than trying to lean over the side as you drive along on a quad.. haha.

The video didn't sound too noisy to me for the distance the phone was away.. There were a couple of what seemed like intermittent clack sounds, but nothing too serious.

I'd do another oil change and then ride it getting used to it and testing things out... As I'm sure you are going to do.