YT175 running with a hiccup - VIDEO

[ddiggerr]

Fired up for the first time after total rebuild. Now I have no idea whats going on. Compression is 120, new plug, new fuel and oil lines, new choke and fresh fuel. Carb cleaned and reeds are good (no gaps).

It fires up first pull and only idles if I play with idle screw. As soon as I touch throttle, it goes bezerk on me and I have to shut it down as you can see in video .......

https://youtu.be/2l1_rXMusaw

You can here the recoil lever tinging in the video. I lost the spring. D"oh!!

Any and all suggestions will be appreciated.

Thanks

[ddiggerr]

Update:
So far I have swapped ignition coil, spark plug, CDI with no change. I have removed flywheel to check keyway and it is where it should be. Stator is also within spec and installed correctly. I have also swapped out jet needle and played around with different settings. Eventually I put it back to the 3rd line.

Will not start without choke and stalls out when choke is off. Played with choke adjustment and doesn't change.

The engine already has new seals and bearing so I am completely baffled as to what I am missing here.

Any takers?

Just went out and swapped carbs from a running YT175. Same results.

Checked resistance on stator ... I get 10ohms +/- 10% on pickup coil within specs as per manual and I get 273ohms on charge coil. Manual states 300ohms +/- 10%, so that is also within spec.

Ugggghh !!!!

[ddiggerr]

Could this be caused from the exhaust leaking where the pipe meets the connection at the engine? I noticed it's blowing exhaust out of there and it is missing what appears to be a ring on the end.

Someone must have seen this happen before.

[ddiggerr]

Nobody?
Surely there has to be someone willing to take a stab at this.

[ddiggerr]

I have given up.

I have exhausted all possibilities as to why this is not running.

I just spent another 2 hours going over everything including the possibility of the exhaust being plugged, it wasn't. I have went over the wiring and found nothing. I have wicked spark and 120 compression. No air leaks. I have spark, fuel, air, compression.

Now it won't even fire without shooting some carb cleaner in the carb. Then it only runs for 2 seconds and stalls out.

It's like it is starved for fuel, however, when I put my hand over carb, it is sucking it in as I have fuel on my hand and I can see there is fuel in the line moving freely.

Almost 400 views and still no reply.

I have found nothing online in the last few days that even resembles the issue I have.

??????????

[madmass]

Is the throttle cable frayed or sticking? Possibly a bent needle hanging up. Have you ran it with the filter on it? Filter between the tank and carb? Seems like you've done a lot of inspection. The only thing I can think of is start back at the basics. Sorry, not much help I know but I have been in your shoes and usually find the issue when I start back at step one. Vaccum pressure in the motor, cables, dirty carb, leaking head gasket... Things like that. Best of luck.

[dgm635csi]

Have you checked the vacuum line that drives the fuel pump? Have you pulled the fuel line off the carb, placed it in a bowl or cup, and pulled on the pull starter? The pulses from the engine should squirt quite a bit a fuel out of the fuel line as the engine is turned over. It sounds like its idling just fine, but not getting enough fuel when the throttle is opened. It also sounds like its running lean from your description about not running when the choke is turned off. You may have a crack in the insulator boot between the carb and head. The choke isn't really designed to be adjustable. The choke on my yt175 is adjusted properly when the locknut is threaded as far out on the adjustment collar as possible, and the collar is threaded as far into the brass choke body as possible until the locknut jams against the choke body. Any air leaks in the choke system, or anywhere on the carb exposed to engine vacuum will wreak havoc on your tuning. Check the O-ring on the choke plunger as well.

[ddiggerr]

Is the throttle cable frayed or sticking? Possibly a bent needle hanging up. Have you ran it with the filter on it? Filter between the tank and carb? Seems like you've done a lot of inspection. The only thing I can think of is start back at the basics. Sorry, not much help I know but I have been in your shoes and usually find the issue when I start back at step one. Vaccum pressure in the motor, cables, dirty carb, leaking head gasket... Things like that. Best of luck.

No frayed cables. No bent needle. Carb is spotless as far as I can see, but will probably clean it again. Haven't run it with filter yet as I should be and have one.

Thanks

[ddiggerr]

Have you checked the vacuum line that drives the fuel pump? Have you pulled the fuel line off the carb, placed it in a bowl or cup, and pulled on the pull starter? The pulses from the engine should squirt quite a bit a fuel out of the fuel line as the engine is turned over. It sounds like its idling just fine, but not getting enough fuel when the throttle is opened. It also sounds like its running lean from your description about not running when the choke is turned off. You may have a crack in the insulator boot between the carb and head. The choke isn't really designed to be adjustable. The choke on my yt175 is adjusted properly when the locknut is threaded as far out on the adjustment collar as possible, and the collar is threaded as far into the brass choke body as possible until the locknut jams against the choke body. Any air leaks in the choke system, or anywhere on the carb exposed to engine vacuum will wreak havoc on your tuning. Check the O-ring on the choke plunger as well.

I ran a line from tank to carb bypassing pump. I left the vacuum line hooked up to pump with fuel lines still hooked to it when I bypassed pump. When I cranked it, whatever fuel was in the lines was spraying out. When I pull the plug to check it, it's like new. A little damp but thats it. Still shiny.

I will need to recheck the choke.

Thanks

Went and checked choke ....... there is no o-ring on the choke plunger and I see no place for one to go

[ddiggerr]

And the saga continues.

I have swapped choke cables with one that has o-ring on plunger. No chang.

The needle was swapped with a new one. No change.

I have eliminated the fuel pump and have added a fuel filter. No change

I have also swapped reeds and boot. Funny thing, the reeds that were on there were in desperate need of being replaced. The ones I put on to test were new.

No change, however, I put the crappy ones on my other trike and they work. In fact I put all the parts I pulled off the non working trike onto the trike that does run. Guess what..... It fires up first pull.

I am officially throwing in the white towel. I need professional help as I have exhausted myself and cannot pull that cord anymore.

[dgm635csi]

First, you should not bypass the fuel pump. There is hardly any height difference between the fuel line on the tank and the carb, so unless the tank is full, there may not be enough fuel flow to the carb from gravity alone. The little pumps are fairly reliable, and easy to repair, or replace.

See the attached picture for choke assembly, and the o-ring on the choke plunger. If this is missing, you will have a large air leak into the engine as air is drawn through the choke assembly into the carb. The choke will also not work properly.

Hope this helps.

[ddiggerr]

Yup. I have one of those on the other trike and tried it with no change.

The PO added the fuel pump to the trike. Everything except the top end, exhaust, carb, and fuel pump is a yt125g.

Checking s/n on engine is from a 1980 yt125 and matches frame.

Am I missing something that would be crucial to make this converted 125 run?

[ddiggerr]

So I have the bare minimum wiring hooked to test this thing.

I cannot find any info on the oil level checker. Since it gets hooked into CDI, if it is not hooked up or detects low oil, does this cause trike to go I to limp mode and also affect starting issues?

It's the only thing I have not checked. Next thing is swapping out stator even though I am showing good spark.

[toki]

welllllll... dunno if any of my rambling will help but here goes my story!

I have an 83 250r. did a COMPLETE rebuild on it. its was trashed when i got it. I spent a TON of money rebuilding it and learned a lot. but every now and then it would start to idle funny. just like your 175. sometimes it was right away. sometimes it was after it was warmed up. I swapped almost everything i could think of. I replaced the head, crank seals twice, almost everything intake related, even the exhaust. and it still did the same trailprotrailprotrailprotrailpro. I purchased another new set of reeds a few weeks ago and had a HARD time getting them to lay flat. it was hard to start and the reeds just didnt look right. then it hit me... the effin reed cage was warped! i lapped it on an "ultra-flat" hunk of marble at work. the reeds looked awesomely flat. and its never ran better.

looking at google images and ebay it looks like the yt175 reed cage is coated in some kind of rubber just like my 250r reed cage is. I think i used 600 grit and then 1000.

maybe you already looked there tho lol. just a thought!

[ddiggerr]

welllllll... dunno if any of my rambling will help but here goes my story!

I have an 83 250r. did a COMPLETE rebuild on it. its was trashed when i got it. I spent a TON of money rebuilding it and learned a lot. but every now and then it would start to idle funny. just like your 175. sometimes it was right away. sometimes it was after it was warmed up. I swapped almost everything i could think of. I replaced the head, crank seals twice, almost everything intake related, even the exhaust. and it still did the same trailprotrailprotrailprotrailpro. I purchased another new set of reeds a few weeks ago and had a HARD time getting them to lay flat. it was hard to start and the reeds just didnt look right. then it hit me... the effin reed cage was warped! i lapped it on an "ultra-flat" hunk of marble at work. the reeds looked awesomely flat. and its never ran better.

looking at google images and ebay it looks like the yt175 reed cage is coated in some kind of rubber just like my 250r reed cage is. I think i used 600 grit and then 1000.

maybe you already looked there tho lol. just a thought!


Ya , I have another reed valve from my other trike that are perfect and it still runs like crap when I swapped it. I am about to go out and swap the last CDI I have from a running trike. I am thinking, hoping, this will do the trick. I would hate to have to tear the motor out again as it was a bear getting everything back in the way it should be and all lined up. I will probably do a leak down test before I do that. I really don't think I have any kind of air leak in the case though, but at this point, anything is possible

Update.... Known working CDI no different. I also rechecked all wiring and compression. Hooked the fuel pump back up as I now know it is needed. It would only fire with a shot of carb cleaner into carb but would instantly die.

Ground is good.

Time to fork out some bucks and have a professional look at it.

[RubberSalt]

What main jets are you running? What plug do you have installed?

on my yt175, I always ran a b8es for the plug gapped at 27 thousands. Home made pipe, 30mm carb, Blaster reeds+ spacer, tripple ported +boyesen ports. only had 100psi on the rebuild lol.

The problem isn't ignition related, it's firing right on que. Either the spark it's to rich or way to lean. Did you do a leak down on this machine after the rebuild?

[ddiggerr]

No leak down test was done. Spark plug is br7es NGK and shoots a nice big blue spark and gapped at .28. I have tried running as stated in manual as well as too lean or too rich. I did have it running but now it won't even fire.

I have a feeling the case has filled with fuel now and not sure how to drain it without flipping trike upside down. No drain hole for crankcase

[RubberSalt]

Pull the plug, post a pic of the tip when you get it out.

I'm putting my money on air/fuel. You either have a big air leak leaning it out, or its running extra rich. You'll need to do a leak down to test this and confirm there are no leaks. If you have a tire guage that can accurately read 5-10psi, then you can build a leak down tool set for less than $10.

The only ignition related part i see it bring.. Is the flywheel securely bolted down? Is it lined up on the keyway?

[Tri-Motor]

Plug should be a BP7ES or Champion N9YC

[ddiggerr]

Plug should be a BP7ES or Champion N9YC

I pulled plug from running trike and it is a BP7ES NGK and still no change.

Just got off phone with Yamaha dealer and they won't touch any tri moto's because they are too old. Thanks for nothing Yamaha.

So I will need to attempt a leak down test on my own. But first I need to put it together somehow

[RubberSalt]

I'll post up instructions and a part list tonight.

You'll need to seal off the exhaust port of the engine. Rubber under the flange works.

Need a way to fill the engine with 7-9psi of air. Tire valve stuck in a PVC end cap works. End cap stuck in the intake boot.

[ddiggerr]

Well, do I ever feel like a dope.

I went out today to look things over. Someone mentioned to check the flywheel (magneto) to see if it different than the one from the running trike. I actually have three.

So, I put all three side by side to compare and they are identical. Next I decide to see if maybe one of the wires from the stator was rubbing and was shorting out. Nope nothing there. After going back and forth between the 2 trikes looking at the stators, I noticed that the pulse coil and source coil was installed differently on the freshly rebuilt trike.

When I put everything back together after cleaning off the crud, I had the wires facing out on both of them, and they apparently need to be facing in. That is one thing the manual does not show. I had actually installed them backwards.

I put everything back together, primed it with a shot of carb cleaner, because I don't have the air box on yet, and it fired up. I threw on the plastics and took off out of the garage.

https://youtu.be/cS23kzpEc4w

Now I just need to take care of the exhaust leak where the pipe meets the engine.

Glad I didn't waste money taking to the dealer.

Thanks everyone for your input.

[RubberSalt]

:)

That sound makes me miss my YT... I need to rebuild it. I'm not sure if i bore it over or not. One of the triple ports dug into the cylinder. The bottom end will also need separated and new bearings+crank bearing. Shattered that piston and locked up the bottom end.

But the blaster engine is almost a drop in on these machines.

[ddiggerr]

So I go back out and try and start it up after it has been sitting for awhile. No go. So I tear off the aif box and bam it fires up. While it is running, I put air box back on and it dies, like it was choked off.

This time I pulled off the top of air box and it started and stayed running.

I went and started the other trike and the same result.

My remedy was to put in a few washers to leave a crack between the halves so there was more air flow and both are running great now.

Strange to me why

[fieldy]

Try some bigger pilot jets?

[RubberSalt]

The air box is plugged up! Make sure nothing is plugfingrhe inputs for the box.

Your patching the problem, not fixing it.

[ddiggerr]

I thought it might be plugged too ... however, I cleaned them out and there is absolutely nothing inside either one of the boxes.

I even pulled out the filters thinking they were restricting air flow.

Seems like they will only run normal with the boxes being slightly cracked open.

The one trike has this design for the air box .....

http://www.partsfish.com/oemparts/a/yam/50038811f870021f60a09831/intake-yt125g-h

The other trike has this design ....

http://www.partsfish.com/oemparts/a/yam/5003882df870021f60a098ef/intake

both trikes were doing the same thing, but are now running with the air boxes cracked open a bit

[ddiggerr]

Finally have it running great now ... Soaked the carb in Seafoam for a few days. While I was blowing everything out, I noticed the small little jet, or whatever it is in the bottom of bowl, looked plugged. I cleaned it up and put everything back together. Fired up 3rd pull with airbox on properly.

Took it for a spin to test the clutch adjustment, but not sure if I have it setup correctly yet, still feels like it slips a bit. Also still need to fix the exhaust leak where pipe joins engine.