What on earth could be wrong with my Tomos?

Quinten Hollering /

-Carbie is clean

-Tank is clean

-Fuel is fresh

Still bogs down at low rpm. Have to very gently roll into it from idle or it just stalls. What I found is that putting on the choke and then gunning it does seem to get it off the line the way it should but it then swiftly dies down again. Once it gets in the powerband it runs fine. It also won't idle properly, RPM drops very slowly and gradually and eventually just comes to a very gentle stop after about 20 or 30 seconds. It's impressive how low an rpm it can run at before stopping completely. A little dab of throttle gets it back up to normal idle speed. Any idea what the issue could be? The entire bike is 100% bone stock, all the mods are visual.

Before this, cleaning the carburettor (and/or the tank) would do the trick. I opened up the carb expecting it to be gross like before, but I apparently did a decent enough job cleaning the tank out cause it's perfectly fine inside. (edited)

Re: What on earth could be wrong with my Tomos?

♣Slew Foot♣ /

Clogged gas cap vent.

Airleak at connector or cyl.

Check the torq on the cyl nuts.

Wear on rings if uber high mileage clutch pads too.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

99.9999% sure it's not the gas cap, where exactly would I have to look for that air leak? It's not that high mileage it's only done about 7300 miles, or 11800 km

Re: What on earth could be wrong with my Tomos?

Common air leak areas would be where the carb meets the intake, intake to cylinder, cylinder base to crankcase and crankcase seals.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

Given how many times the carbie has come off I immediately suspect the first. If that's the culprit, how would I got about fixing it?

Re: What on earth could be wrong with my Tomos?

The easy way to test is to give it a shot of carburetor cleaner at the clamp and see if the rpm changes. The cause is usually a worn shim or the rubber gasket behind it.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

There is a nylon ring between the carb and intake, could be that. I'll check and report back, I'm guessing local shops will stock new ones.

Re: What on earth could be wrong with my Tomos?

Try a viton o-ring in there if those crazy original seals aren't available

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

I will, but I assume local shops should have plenty of parts like these. They usually do, I got a new throttle handle and air filter there as well.

Re: What on earth could be wrong with my Tomos?

I would get that carb back off and the intake this time to inspect he reed block. The reeds may be sticking, or they may actually be bent and not closing fully. If you look thru the underside at a light and can see any light coming in thru the edges of the reeds then they are not fully closing. This will cause undesired effects to your throttle range and responce. They can usually be removed by the screws and flipped if they are only slightly bent. But you may need some new reeds.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

It's a 2008 model so theoretically it shouldn't be too bad but if the nylon ring doesn't fix it I'll make sure. It feels a little down on torque, could that be a sign of bad reeds?

Re: What on earth could be wrong with my Tomos?

If it's a 2008 it should have the A55 with a spigot mount phbn and rubber intake boot so it wont have the nylon bushing. You should still check for air leaks though.

Re: What on earth could be wrong with my Tomos?

> Thomas Smith Wrote:

> -------------------------------------------------------

> If it's a 2008 it should have the A55 with a spigot mount phbn and

> rubber intake boot so it wont have the nylon bushing. You should still

> check for air leaks though.

WRONGO.

he's got an a35 quaddro, a euro bike. they stuck with the SHA and a35 cylinder setup for a while.

Re: What on earth could be wrong with my Tomos?

My bad, I should have looked at the profile.

Re: What on earth could be wrong with my Tomos?

Overpriced Parts /

Not tuned correctly! You got to learn how to tune .

If I had a bike for a part of a afternoon It would rip !

Tuning is not as hard as it seems!

Re: What on earth could be wrong with my Tomos?

♣Slew Foot♣ /

The slow into first sounds like a clogged cap vent. Try without cap on.

The reeds could be slightly misaligned but it wouldn't start right up. Same if there was a big enough airleak.

If You have a freakishly long intake or huge intake it could be a gasket or seal and still run.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

> LSLB RXb Wrote:

> -------------------------------------------------------

> WRONGO.

>

> he's got an a35 quaddro, a euro bike. they stuck with the SHA and a35

> cylinder setup for a while.

It's supposed to be an A35 but the engine does say A5 and A55 in a number of places, the carbie is if I'm not mistaken a Dell'orto SHA 14/9.

> Overpriced Parts Wrote:

> -------------------------------------------------------

> Not tuned correctly! You got to learn how to tune .

>

> If I had a bike for a part of a afternoon It would rip !

>

> Tuning is not as hard as it seems!

It ran fine on this tune a while ago so I doubt that's the issue.

> ♣Slew Foot♣ Wrote:

> -------------------------------------------------------

> The slow into first sounds like a clogged cap vent. Try without cap on.

>

> The reeds could be slightly misaligned but it wouldn't start right up.

> Same if there was a big enough airleak.

>

> If You have a freakishly long intake or huge intake it could be a gasket

> or seal and still run.

I tried it without the cap and it made no difference. And yeah it starts cold first kick so that makes it sound like it isn't the reeds. The intake isn't suuuper long but it definitely isn't short either. Probably 5 or 6 inches or so. The carbie on these is next to the frame instead of below it, makes it a breeze to work on if nothing else :p I'll give it the brake cleaner test tomorrow but when I think about it I'm almost certain it's that nylon ring. The two halves of the "clamping" part of the carburetor are touching, and I can still "twist" it on the intake by hand. It won't come off or anything but I did have some concerns that it wasn't clamping down hard enough. (edited)

Re: What on earth could be wrong with my Tomos?

♣Slew Foot♣ /

14 12 is stock carb.

Upjet a size or 2 . ditch oil imjectors thingy. premix 50.1. Lose restrictive airbox block hole in intake.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

> ♣Slew Foot♣ Wrote:

> -------------------------------------------------------

> 14 12 is stock carb.

>

> Upjet a size or 2 . ditch oil imjectors thingy. premix 50.1. Lose

> restrictive airbox block hole in intake.

I checked and you're right about the carb. Mine don't have the oil injector thing though, that was an option I believe. I already run 50:1 premix. By the restrictive airbox block hole do you mean opening up the (for lack of a better term) d-shaped intake? I know it ran great on this jet before so I'll wait with upjetting until I have it back to running how I know it's supposed (and able) to. (edited)

Re: What on earth could be wrong with my Tomos?

Leave the airbox, they do a lot for longevity vs the measly "performance" increase you get from running with out one. (not to mention having to rejet with every 8-10ºc temp change you encounter)

oil injection is fine too. there is a customer at my shop who rides between 200 to 400 miles per week with an a35 tomos with the stock cylinder, a hunter pipe and the stock sideshot intake and stock airbox with the oil injection still working. He's put probably 2,500 miles on the bike since he bought it in November 2020. He even rode it from Boston to Hartford and back last weekend, something like a 200 mile round trip.

my point is there is no need to deviate from what Tomos put on there. The stock airbox is great. its all great.

you might just need to turn up your idle screw a 1/2 turn?

Re: What on earth could be wrong with my Tomos?

♣Slew Foot♣ /

No if it was injected they block the hole in the intake with a screw or bolt it maybe loose or missing. The airbox ditch and use a highflow filter or metal disk.

But seriously the gas cap vent check it cause the main symptom is holding in 1rst gear and not shifting due to low rpms cause of lack of fuel.

It could be a passage in the banjo to floatbowl float pin or the vertical tube or even the holes in that tube. It could be the internal petcock filters length of fueline inline filters and diameter of fuelline. It sounds as tho it is fuel staves on take off restriction in fuel flow go from there be warned carb problems are often electrical gremlins and vice versa.

Re: What on earth could be wrong with my Tomos?

♣Slew Foot♣ /

My carb is open. I have never got anything in it. Anything hard enough or big enough would get caught in the reeds.

Yea ok if you are in really dusty places or the desert I would put a shirt w a rubber band over it.

I upjet from 74 to a 75 when it gets below 32f.

Re: What on earth could be wrong with my Tomos?

I have never been able to tune a sha without some sort of airbox on it. It has to have some kind of direct flow or restriction on it or they just dont ever seem to want to function thru the throttle range.

Re: What on earth could be wrong with my Tomos?

Have you considered it's something not of this earth?

That's all I came here to say.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

> LSLB RXb Wrote:

> -------------------------------------------------------

> Leave the airbox, they do a lot for longevity vs the measly

> "performance" increase you get from running with out one. (not to

> mention having to rejet with every 8-10ºc temp change you encounter)

>

> oil injection is fine too. there is a customer at my shop who rides

> between 200 to 400 miles per week with an a35 tomos with the stock

> cylinder, a hunter pipe and the stock sideshot intake and stock airbox

> with the oil injection still working. He's put probably 2,500 miles on

> the bike since he bought it in November 2020. He even rode it from

> Boston to Hartford and back last weekend, something like a 200 mile

> round trip.

>

> my point is there is no need to deviate from what Tomos put on there.

> The stock airbox is great. its all great.

>

> you might just need to turn up your idle screw a 1/2 turn?

Yeah I was hesitant about modding stuff cause I know it runs fine in stock form and I'm not looking for extra performance. I'm much like the customer you mention, though my commute is shorter. I also don't have oil injection (didn't come with it), though if nothing else I'd have been forced to get rid of it with the mods I have planned so maybe it's a good thing cause it means I can keep it mechanically stock. It's not idle, I actually raised it a few whole turns in an attempt to compensate but it didn't really help.

> ♣Slew Foot♣ Wrote:

> -------------------------------------------------------

> No if it was injected they block the hole in the intake with a screw or

> bolt it maybe loose or missing. The airbox ditch and use a highflow

> filter or metal disk.

>

> But seriously the gas cap vent check it cause the main symptom is

> holding in 1rst gear and not shifting due to low rpms cause of lack of

> fuel.

>

> It could be a passage in the banjo to floatbowl float pin or the

> vertical tube or even the holes in that tube. It could be the internal

> petcock filters length of fueline inline filters and diameter of

> fuelline. It sounds as tho it is fuel staves on take off restriction in

> fuel flow go from there be warned carb problems are often electrical

> gremlins and vice versa.

I did check, I promise it's not the gas cap vent :p I have some suspicion of the fuel itself rather than the amount thereof but I can't fully rule that out just yet. I'll let you all know. Some gas stations here offer ready-made 50:1 premix. The benefits are that you don't have to mix yourself but more importantly to me a lack of ethanol. The biggest downside is that it doesn't quite get as much use as the others (most moped tanks are only around 1 or maybe 2 gallons after all) so the fuel in there can be pretty old in some cases. Thankfully they made sure the oil doesn't settle and mess up your mixture. (edited)

Re: What on earth could be wrong with my Tomos?

Je moet altijd oppassen met brommix pompen die handmatig gevuld worden, ik heb al wel eens meegemaakt dat een pompbediende vergeten was olie in dat ding te gooien. Niet dat dat nu je probleem is, maar dus altijd even kijken of de kleur een beetje klopt en bij twijfel zelf nog een scheutje olie toevoegen.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

> Bas Autowas Wrote:

> -------------------------------------------------------

> Je moet altijd oppassen met brommix pompen die handmatig gevuld worden,

> ik heb al wel eens meegemaakt dat een pompbediende vergeten was olie in

> dat ding te gooien. Niet dat dat nu je probleem is, maar dus altijd even

> kijken of de kleur een beetje klopt en bij twijfel zelf nog een scheutje

> olie toevoegen.

Ja die mijd ik als de pest, degene die ik gebruik wordt niet met de hand gevuld

Re: What on earth could be wrong with my Tomos?

"Almost runs good if preloaded with choke" Cant believe no one mentioned it but this tell me your idle circuit on your sha carb is partially clogged, run a small stranded wire thru it 12 times. Fuel stabilizer helps as well as actually cleaning your petcock and fuel banjo.

Re: What on earth could be wrong with my Tomos?

Quinten Hollering /

> pat splat Wrote:

> -------------------------------------------------------

> "Almost runs good if preloaded with choke" Cant believe no one

> mentioned it but this tell me your idle circuit on your sha carb is

> partially clogged, run a small stranded wire thru it 12 times. Fuel

> stabilizer helps as well as actually cleaning your petcock and fuel

> banjo.

I'll see if I can find it. I did clean the banjo and petcock, so don't worry about those.

Re: What on earth could be wrong with my Tomos?

Try revving on the stand.

If it doesn’t bog it’s your clutch.

If you clutch engages super early or hangs up it’ll act crazy like this

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