Summit 175 - Unwanted Engine Braking

Sailor15 · Mar 31, 2018

Hi All -

Riding a 2015 800 174 and 2018 850 175, lots of trading back and forth this weekend and noticed a large difference in the way the two sleds react to letting off the gas. The 800 feels like an automatic car, gliding as the gas is let off. The 850 feels like a manual accelerated and then let off the gas in a low gear, throwing you forward towards the handlebar due to the engine braking - not fun!

Any ideas what may be causing this? Sticking primary? Wrong clutch settings? Expected behavior of the 850?

Thanks!

toyotamobbin · Mar 31, 2018

Umm that’s a good thing in my opinion. I cluched my sled to backshift even harder, it helps in the trees and it helps slow you down dropping down steep hills.

ak · Apr 1, 2018

If you don’t like it don’t ever buy a I backshift clutch kit. There’s lots of engine breaking.

Do you know what clutching is in the sled?

Barcode · Apr 1, 2018

Try to adjust the secondary so the belt sits lower in it. We noticed the same thing on ours.

Adam12 · Apr 1, 2018

Barcode said:
Try to adjust the secondary so the belt sits lower in it. We noticed the same thing on ours.

Wouldn't this speed up belt wear?

slednfool · Apr 1, 2018

Yes. Builds more heat with the slipping and lost performance too.

Barcode · Apr 1, 2018

I personally can't say for sure if it does or not. But this is exactly what I was told by Joey (iBAckshift) to do to help with toning down the backshifting. It works.

Sailor15 · Apr 1, 2018

Thanks for the thoughts everyone. While I can appreciate that it might be beneficial in the technical stuff for better track control, as a still fairly new rider its been a bit of a handful.

How would one go about lower the belt in the secondary? Any other ways to reduce backshifting without robbing performance?

ak · Apr 1, 2018

Sailor15 said:
Thanks for the thoughts everyone. While I can appreciate that it might be beneficial in the technical stuff for better track control, as a still fairly new rider its been a bit of a handful.

How would one go about lower the belt in the secondary? Any other ways to reduce backshifting without robbing performance?

https://m.youtube.com/watch?v=Q2FvMD41jCw

I wouldn’t run the belt to loose it will start rubbing on the belt guard and footwell area.

On a 2018 with the 531 belt you should see the cord on the side of the belt level with the top of the secondary clutch to be adjusted correctly.

IcutMetl · Apr 2, 2018

Subscribed.

Want to get a clutch kit for my ‘19 FreeRide. I like a lot of engine breaking, and wondering how the different kits compare with each other. There’s so much going on with ramps it seems like; profiles, medthod & positioning of weight, etc.

ak · Apr 2, 2018

IcutMetl said:
Subscribed.

Want to get a clutch kit for my ‘19 FreeRide. I like a lot of engine breaking, and wondering how the different kits compare with each other. There’s so much going on with ramps it seems like; profiles, medthod & positioning of weight, etc.

I backshift (dynamoe joe) clutch kit has lots of engine breaking.

toyotamobbin · Apr 2, 2018

IcutMetl said:
Subscribed.

Want to get a clutch kit for my ‘19 FreeRide. I like a lot of engine breaking, and wondering how the different kits compare with each other. There’s so much going on with ramps it seems like; profiles, medthod & positioning of weight, etc.

I like roosterbuilt clutching. Lots of back shift and a smoother engagement then stock which I think helps keep traction in technical sections. Throttle response to track is also improved.

MSP381 · Jan 1, 2019

I have the DJ clutch kit and I am too noticing a huge amount of engine braking caused by the back shift. It is really smooth but man I barely use the brakes. I am just getting back into riding and it is a handful to learn the new platforms and shifting is something to learn. Not sure if I like it at this point but I have a lot to learn and need a lot more riding time. I hope it gets better and easier to learn.

NoSoup4U · Jan 1, 2019

Engine breaking is the result of strong secondary clutch backshift, and strong back shift is considered a positive attribute in a mountain sled setup for boondocking and deep powder. It gives instant throttle response and consistent RPM when in and out of the throttle, and strong engine breaking makes it much easier to control the sled coming down steep hills than clutching that "coasts" and you can only use the brakes to control speed. Trail sleds are typically clutched to "coast" more than mountain sleds.

Backshift is controlled by the secondary clutch, and if you want weaker backshift you would either put in a softer secondary spring or steeper helix. In mountain riding this would likely result in slower throttle response, inconsistent RPM, and increased clutch heat. Note that if you change either the secondary spring or helix you will also likely have to make adjustments to the primary clutch since peak RPM will also be affected.

PaulAnd · Jan 1, 2019

You want engine braking! That’s a good thing, get used to it!
You also want the belt as tight as possible, don’t lower the belt into the secondary unless you want to blow it!

Sent from my iPhone using Tapatalk

live2beel · Jan 1, 2019

I must be out of the norm also. I hate hard engine braking also.

MKULTRA · Jan 1, 2019

live2beel said:
I must be out of the norm also. I hate hard engine braking also.

I would guess guys who don't like "engine braking" which is in fact clutch braking and riding in very open areas.

Matte Murder · Jan 1, 2019

First ride on my18 175 after the engine mounts and primary spring update. The engagement is late(4000 rpm) and harsh and the back shift is REALLY strong. Stronger than any Roosterbuilt clutch kit I’ve had. It works great in the powder but was harsh on the trail and packed down single track. Trying to learn to ride around it with smoother throttle manipulation and anticipating it so I get braced a little. It def makes the sled more physical to ride. There’s backshift and now super backshift lol.

Dynamo^Joe · Jan 1, 2019

Engine braking strength is based on….

Maximum engine vacuum
Primary spring start force
Secondary spring start force
Primary clutch ramp angle (first 1/5th of the ramp)
Drive belt width (wider = stronger, narrower = less strength) More belt gap, less strength,

Adjusting those details above change the de-clutching speed.

The engine should idle at 1100 to 1200 rpms.
Logic statement; IF the engine is idling higher than 1200 (ie 1400), THEN engine braking strength will be lower than 1200.
Maximum engine vacuum is at the lowest idle speed. (etec can only be adjusted by BUDS laptop)
Open the throttle plates more, vacuum drops, engine braking strength lowers.
If there is an air leak (reed boot or crank seal) causing engine speed to idle high like over 2000 rpms, there will be nearly no engine braking whatsoever.

Secondary spring – can increase the start force for stronger engine braking. Can lower start force to reduce strength.

Belt tension – Maximum engine braking is when you can make the belt deflection be not quite as tight as this but dang close.
https://www.youtube.com/watch?v=VNVv-jOzaIE

Right now with a stock 800etec and 850etec, about the only details you can do to lower engine braking strength is...
1] dial in a little bit more belt deflection (make the belt sit slightly lower in the secondary) by turning the belt adjuster about 1/12 of a turn - like turning it from 1200 to 100 (drop the belt a little)

2] lower the start force of the secondary spring (but i would not on a summit, 160 start is low enough

3] Get someone with BUDS to increase the engine idle up 200~300 rpms. [easily done on a carb jobby]

4] Go from the 417300531 or 571 @ 38.3mm to the narrower 572 belt @ 37.7mm

On my clutch kits...

Dial in a little bit more belt deflection; make the drive belt ever so slightly more loose tension between the pulleys.
I also have secondary clutch spring start force options from 225/XXX to 195/XXX
I can also provide a shim to raise engagement speed by 200 rpms.

My latest testing of the new 966 ramp with 31~3200 engagement when i was out in Revelstoke first week of Dec, tree riding; I could come down a fairly steep hill on someone else's track and the engine braking held till about 12kmh (8mph) before de-clutching....hahaha.

BIG JOHN · Jan 4, 2019

Sailor15 said:
Hi All -

Riding a 2015 800 174 and 2018 850 175, lots of trading back and forth this weekend and noticed a large difference in the way the two sleds react to letting off the gas. The 800 feels like an automatic car, gliding as the gas is let off. The 850 feels like a manual accelerated and then let off the gas in a low gear, throwing you forward towards the handlebar due to the engine braking - not fun!

Any ideas what may be causing this? Sticking primary? Wrong clutch settings? Expected behavior of the 850?

Thanks!

both secondaries set up the same (QRS, 40, blu/blu)...
TRA vs Pdrive is main diff...
the 175 has 200/400 spring (ridiculously wrong)...
easy fix is a 170/400 if you want to try something...
I recommend a stiffer sec spring too...
or call for known/proven "kit"-BJ

Summit 175 - Unwanted Engine Braking

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