KTM starter - how to get more cranking power?

I've got a challenge. I need to start a motorcycle engine. It's a KTM 600cc or so. Unfortunately the starter does not have enough power to crank it fast enough for a reliable start. While it is apparently a factory race engine I don't really have any motorcycle expertise. Is it possible or common to be able to purchase high performance starters to crank something with a higher than normal compression ratio? The wiring is good I just need a stronger starter. Any ideas?

-Michael

[NoLimits]

If the compression hasent been bumped up, make sure the decompression lever is working (if it has one), if not, not much you can do, KTM parts are expensive as hell.
Push it down the road and dump the clutch in 4th, or kick it, but make damn sure its passed tdc, or you will end up over the bars.

Yes it has a decompression lever and it works but this is in a different sort of vehicle and the lever is unavailable. The car has to be able to start with the driver in so we're limited to an electric start. It has a recluse (sp?) clutch in it so you can't even bump start it.

-Michael

[NoLimits]

Try woodies in perth, but if comp. has been bumped way up, be prepared to pay, if no heavier starter is available, big singles you have to have the decompression system working or a 200lb/ft starter. (more than a v8)

I didn't know it was that hard to start a motorcycle. Yes it's a big single cylinder. This is for the FSAE car so I think they actually have a sponsorship with woodies. First thing I told them was bigger starter wire it's about 10ga right now. I can't make it start for them if they can't make it crank for me...

-Michael

[Domo]

Get a larger flywheel on that bad boy, and find a way to make the decomp. lever functional. Use an electric starter from a 4-stroke snowmobile, like the RX-1. (1000cc 4-stroke engine) This is what the Mech Engineering kids at UofT did on their Formula SAE car a couple years back.. Seemed to work well.

Michael,

If the driver isn't able to reach the compression release, what about either a bicycle line to a small lever in the cockpit (huhuhuhhuh) or a solenoid? I bet a power door lock solenoid would have enough juice. Then you could do it (hihihihi) remotely.

Well 2 things about the decompression level. First it doesn't seem to fire with the lever depressed but it speeds up cranking and fires as soon as I let go of the lever. The second thing is that they "didn't want to" hook it up. I figured that they could get around it by just finding a performance starter but since I'm not into motorcycles I just didn't know...

-Michael

[b18a1+gsr-trans]

24v starting system

2 12v batteries in parallel for running/charging, switched to series via a relay for 24v starting only.
or
find a high enough energy fuel to inject on startup that will blast that piston down with enough force to recompress the second fire cycle, but this would require a secondary injection system to be fabricated. solenoids, nitrous or either or something else? map gas?, lines, ect.

if they dont want to start it properly, then you have to start it not properly lol, engine/part longevity must not be a priority

[b18a1+gsr-trans]

and for this last suggestion i will require a blow job :lol:

put a choke on the intake, a old throttle body that is machined for a IACV and epoxy that channel shut (throttle bodies with an IACV have a much better sealing throttle plate i have found, or maybe its a Japanese thing).

use the idle control bypass screw to set your choke level.

you could set up the bypass screw so it fires while choked, and the solenoid used for the throttle body actuation could be triggered by a circuit that only goes "high" when 13.3v or more is present in the charging system.

this would make the choke fully automatic and quite easy to start on 12v with no extra driver intervention other than turn key

The purpose of a choke is to enrichen the startup mixture on a carb'd engine. This one is EFI using a motec. We've had a lot of trouble with the throttle body design as the fellow who designed it did not take into account the forces applied to the throttle plate. I don't think completely sealing off the intake makes any difference on the cranking speed.

Mainly I need to make it crank easier so I can work on the cold startup part of the map.

-Michael

[b18a1+gsr-trans]

The purpose of a choke is to enrichen the startup mixture on a carb'd engine. This one is EFI using a motec. We've had a lot of trouble with the throttle body design as the fellow who designed it did not take into account the forces applied to the throttle plate. I don't think completely sealing off the intake makes any difference on the cranking speed.

Mainly I need to make it crank easier so I can work on the cold startup part of the map.

-Michael


your not thinking "outside of the box"


a choke will restrict the air intake, your cranking speed is slow because of the compression at TDC.

the intake valve(s) must close with the cylinder still under vacuum (hence the choke). Cylinder compression at TDC will be much lower and you could adjust the bypass screw to fine tune this "vacuum condition" i can assure you 100% that will make it crank faster.



less air in the cylinder, less compression at TDC, faster cranking, if you seal off the choke completely then your force will be in the intake stroke and instead of hearing the starter strain every time it hits TDC, with a sealed choke it will sound like that on the intake stroke instead, use the bypass screw to adjust this for optimal compression and cranking speed.

i will need that blow job now

I can assure you with no air in the cylinder you're not going to get that nice little bang to make things start. They've put the engine back on the dyno so I'll try it this weekend.

-Michael

[b18a1+gsr-trans]

I can assure you with no air in the cylinder you're not going to get that nice little bang to make things start. They've put the engine back on the dyno so I'll try it this weekend.

-Michael




the trick is gonna be the fine adjustment of the bypass screw on the 2nd throttle body so it doesnt block off the air completely, just so it lets in just enough to fire, and it wont be as difficult to recompress the second fire cycle aswell because of the sustained vacuum. i guess it will be easiest to start with it fully sealed, then slowly start opening that choke bypass screw till it fires.

fuel mix during startup will need to be recalculated because as you mentioned before, this will richen it up quite a bit

Sorry you are wrong. Tried cranking it with the throttle all the way closed. Did not make any difference on the cranking speed. Tried it with the throttle all the way open - still no speed. Also, bear in mind I'm experienced at tuning engines here so the throttle position was set correctly from the beginning. The re-wiring of the starter did seem to help a bit though.

-Michael

[b18a1+gsr-trans]

i was actually talking about blocking off the entire rpm control throttle body with a 2nd "dummy" throttle body

more restriction than the stock throttle body can create, also keep in mind with my idea you create a type of vacuum regulator for the intake (passing air through a restrictor(1) then through a variable restrictor(2) can have a pressure or vacuum regulating effect)


if there is no air to compress, how can it be hard to crank? did you try sealing off the intake with your hand?

if the intake manifold is allowed to hit atmospheric pressure between intake cycles, you will loose this effect entirely and it will be difficult to compress, this is why you need vacuum on the other side of the TB aswell so the manifold cant reach atmospheric between intake cycles

(1)rpm control TB, idle bypass airway, correctly set for idle

(2)2nd choke TB bypass to be adjusted

I put my hand over the throttle body inlet. It's enough vacuum to stall the engine dead. If there is no air to compress then you're not going to encounter any resistance on compression but on the intake stroke it must put enough resistance on it. I'm not sure if the amount of energy required to create 12:1 ratio of vacuum or 12:1 ratio of compression is exactly equal but after you pass TDC the pressure in the cylinder should help the crank to move faster until the exhaust valve opens.

The rules forbid having a second throttle plate or any electronic air control. Besides the sealing on the throttle body we have is more than enough to stop the engine dead. I think as Mike said the only way is to get the decompression lever working.

-Michael

[blackfoot]

id love to see this "buggy" these guys have made

i have a lot of bike experiance.. mostly 2 stroke tho.. but im sure theres a fairly simple way to get the decompressor working

[b18a1+gsr-trans]

I put my hand over the throttle body inlet. It's enough vacuum to stall the engine dead. If there is no air to compress then you're not going to encounter any resistance on compression but on the intake stroke it must put enough resistance on it. I'm not sure if the amount of energy required to create 12:1 ratio of vacuum or 12:1 ratio of compression is exactly equal but after you pass TDC the pressure in the cylinder should help the crank to move faster until the exhaust valve opens.

in theory it should, but in application you loose momentum, the compression causes a fast, slow, fast, slow, fast, slow motion on the crank, if you decrease the pulsations you attain a mean (math, not coolness :) ) rpm, which is faster than the slow pulsations


The rules forbid having a second throttle plate or any electronic air control. Besides the sealing on the throttle body we have is more than enough to stop the engine dead. I think as Mike said the only way is to get the decompression lever working.

-Michael


ahhh, cool

didnt know there are rules for that type of mod, and i just meant more of a seal than the stock TB because the stock one should be set for idle, anyway, guess it doesnt matter.

my door popper solenoids are rated for 90lbs pull force and draw about 12A, (ebay solenoids)

maybe connect a ebay popper solenoid to the starter relay to trigger the popper to pull the lever only while cranking? that would make it automatic aswell.

[blackfoot]

i have a 01 XR650L. its a single bore 650cc honda motor.. it doesnt have a decompression button.. would the starter from the honda bolt on the ktm engine?

[blackfoot]

also i learned that my 650 is a bitch to start.. ALL the time!.. it starts great though when the fuel is primed. maybe add a primer? fuel isnt getting to the carb fast enough on start up?


my trick to priming my carb was to tilt my bike over so the float bowl would fill up.. not too easy in a buggy

This is not a carb'd engine. The trouble is that we need it to crank so I can get the cold startup working well. The guy who is on the engine team has been doing a pretty good job and they have some electrical issues - I just thought I'd ask around if anyone had any good secrets.

-Michael

[shiznit]

i have a 01 XR650L. its a single bore 650cc honda motor.. it doesnt have a decompression button.. would the starter from the honda bolt on the ktm engine?


The decompressor is built into the cam on most single cyl. Hondas
I have a trx450R and the decompression assembly sits on the end of the cam.
Works by centrifical force, and hold the 2 exhaust valves open slightly until the motor reaches a certain RPM.